I understand the first past the post system in that the candidate with the most votes in a constituency is elected as the MP for their particular party, but what I don't understand why the SNP can get 40 odd seats with around 3% votes yet the Greens get 1 seat for 1.7% of the vote?

This is not proportional and I don't understand the constituency bias? Can someone explain this please?

  • 4
    Can you provide some context as to what election you’re talking about? Since it sounds like you’re asking a question about a specific election, providing a link to results of that election would help us understand your question better.
    – divibisan
    Commented Dec 10, 2019 at 20:20
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    Look at Germany as an example of voting for candidates with a majority in constituencies and having proportionality too. FPTP is not proportional. UKIP had 12% of the popular vote in 2015 and not a single seat as far as I remember. Commented Dec 10, 2019 at 22:13
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    Does this answer your question? What are the disadvantages of first-past-the-post electoral systems? Commented Dec 11, 2019 at 12:34
  • An overview of the pro-PR point of view which goes into the substantial flaws of FPTP from a UK perspective can be found on Make Votes Matter
    – Jontia
    Commented Dec 11, 2019 at 13:07

3 Answers 3


First past the post is not meant to be proportional. You didn’t say which particular election you were talking about, but taking the 2017 election as an example, the SNP fielded candidates in all 59 seats in Scotland, winning in 35 of them, and achieving 37% of the votes cast in the seats which they contested.

This is a comparable percentage-vote to seat ratio as the overall UK winners of that election, the Conservatives, with 42% of the UK vote share for just under half of the seats they contested.

The Greens, however, achieved just 2.2% of the vote in the 457 seats they stood in.

The answer to your specific question, then, is that the SNP’s votes are far more concentrated in a small number of seats, while the Greens votes are spread around most of the UK. This can be seen as either a weakness or a strength of FPTP - but that’s not the question today.

For an example of a real tragedy of FPTP - and possibly a better example of the phenomenon you’re describing - we need only look back to the 2015 election, where UKIP achieved 12.6% of the UK wide vote-share, but only won 1 seat in Parliament. The feeling of disenfranchisement and unfairness caused by that result could well have been a significant factor in the events that would follow in the Brexit saga.

  • While not part of the question a quick explanation of Gerrymandering could help explain it. en.wikipedia.org/wiki/Gerrymandering
    – Joe W
    Commented Dec 10, 2019 at 21:03
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    @JoeW I’m not sure Gerrymandering is completely relevant in this particular case - the term seems to me to indicate some form of wrongdoing or tactical arrangement of constituency boundaries in order to wrongfully win seats. In this case, the SNP achieved about the same vote-percentage to seat ratio in the seats they stood in as the Conservatives. That doesn’t seem unfair to me; as the SNP is only a Scottish party, it makes sense that they only stand in Scottish seats. It’s not like the SNP gerrymandered the Scottish seats to win 35 seats with only a couple of percent of the Scottish vote.
    – CDJB
    Commented Dec 10, 2019 at 21:09
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    Gerrymandering is not a significant problem in the UK because there's an impartial boundaries commission and boundaries change very rarely. There's no funny shaped US style constituencies.
    – pjc50
    Commented Dec 11, 2019 at 5:30
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    I tend to agree with your final paragraph. The FPTP system bears a lot of the responsibility for Britain's broken politics. It is not such a problem in the United States, since by and large that country still has a two-party system. But FPTP has become less relevant in Britain than it once was, as multiple parties have arrived. Had UKIP been rewarded with seats in Parliament, it would have enabled a national debate better to have taken place on Brexit, so that the issue could have been settled short of a referendum. And referendums do not co-exist easily with parliamentary government.
    – WS2
    Commented Dec 11, 2019 at 23:44

The first past the post voting system favours large nationwide parties (in the UK the large nationwide parties in terms of members, funding and presence in the field are the Conservatives and Labour, to a lesser extent the LibDems) and small parties with strong support in clearly defined regions. The latter group contains almost all of the small or small-ish parties that hold seats in Westminster:

  • The SNP in Scotland (although they have surpassed the LibDems in seats won last election so they happen to be the Third Party in the 2017 parliament)
  • Sinn Féin and the DUP in Northern Ireland (the former do not take their seats but still won 7 of the 18 they contested indicating significant support for the absentionist policy) although it is important to note that the largest parties in Great Britain typically do not field candidates in Northern Irish constituencies; and
  • Plaid Cymru in Wales

Lady Hermon, a Northern Irish indepent is somewhat of a special case: she was initially elected for the Ulster Unionist Party in 2001 but sat and stood as an independent candidate since 2010. She was obviously sufficiently popular in her constituency to continue getting elected even without party support, although the UUP would be another of the local Northern Irish parties. She is not standing for reelection in the 2019 election.

The Greens don’t have a clearly defined local stronghold base. If anything, Brighton Pavillion, the constituency of Caroline Lucas might be considered one as she won an absolute majority there in 2017 when she was still co-leader of the party. But if you take a look at the map of strongest third party by constituency below (taken from Wikipedia, where a full list of authors is available), you see that the strongest third party was LibDems or UKIP pretty much all across England.

UK constituencies by strongest third party
Map of UK constituencies by strongest party that is not Labour or Conservative in the 2017 election. Colour code: orange = LibDems, purple = UKIP, light green = Green party, mid-green = Sinn Féin (NI only), dark green = Plaid Cymru (Wales only), dark blue = National Health Action, light blue = Yorkshire first (Yorkshire), brown = North East Party, yellow = SNP (Scotland only), the other colour in Northern Ireland = DUP (NI only), bright orange = Liberal Party

The map clearly shows how the SNP outscores everything that is not Labour or Conservative across most of Scotland while Plaid Cymru does the same in Wales. However, in Wales there was still much more support for the two main parties leading to Plaid Cymru only gaining 4 seats. The greens pop up in a number of unconnected constituencies as do some exceedingly minor parties in other places (whose names and colours I had to look up). While the UKIP was, at the time of the 2017 election, gaining traction all over England, they never managed to take over a seat from one of the two larger parties (one may argue how much of an opponent the LibDems were after their humiliating defeat in the 2015 election).

Thus, the non-proportional FPTP system favours a party such as the SNP but disfavours one like the Greens or the UKIP.

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    "to a lesser extent the LibDems" - Is entirely inaccurate. An 8% vote share becoming a 2% seat share is not "favoured" by any stretch of imagination. The rest of the answer is on target though.
    – Jontia
    Commented Dec 11, 2019 at 12:59
  • @Jontia I meant that the LibDems be one of the larger parties as they have the ability to field candidates all across Britain and have previously won seats from all over the island to the best of my knowledge. This is why I contrast them to the SNP which, if at all, are only large in Scotland.
    – Jan
    Commented Dec 11, 2019 at 13:25
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    I don't think that came across very clearly if that is what you meant. It sounded like you were suggesting FPTP favoured the LibDems, when in reality it hurts them as much as it hurts the Greens, UKIP and others.
    – Jontia
    Commented Dec 11, 2019 at 13:45
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    Caroline Lucas is no longer the joint leader of the Green Party, the leaders are Jonathan Bartley and Siân Berry: en.wikipedia.org/wiki/Green_Party_of_England_and_Wales
    – PandaPops
    Commented Dec 11, 2019 at 14:29
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    @PandaPops Fixed!
    – Jan
    Commented Dec 12, 2019 at 16:10

Because the UK first past the post system rewards local concentration of support not widely spread but diffuse support

The core answer to the actual question is built-in to the design of the UK's electoral system. It deliberately ignores any consideration of proportionality at the aggregate level (or, perhaps, the complaints of unfairness have never gained enough support for a major party to try changing the ancient system except for the coalition government who proposed a more proportional system and decisively lost a public referendum on the topic). The biggest argument for holding with the current system is that it magnifies swings in the vote and makes getting a government with a decisive majority more likely.

But the mechanics of First Past the Post (FPTP) are clear. The only vote that matters is in the individual seat. A candidate is elected to be an MP if they get more votes than any other candidate in that seat.

So concentration of vote matters a lot. Popular candidates can beat big parties if they can get a strong local vote (this is why the greens get a seat). Parties who spread their vote efficiently (so not building up very large majorities in the seats they win) can win a bigger proportion of seats than their national vote would suggest (this is a current problem for Labour as they have a number of seats in deprived cities where they wastefully get >70%).

So imagine a centre party with evenly spread support across the country of 34% can get no seats at all: in left-leaning seats where the Labour party gets at least 35% will win that seat; in right-leaning seats the Conservative party can win with 35% of the vote. If we assume that the Conservatives and Labour get few votes in the "enemy" seats this could give a parliament where a government gets a majority with ~17% of the national vote (assuming nobody in Labour-leaning seats ever votes Conservative and other parties take up the slack). This is an unrealistic extreme example, but highlights the point.

In reality there are local parties who have few national votes but whose vote is very concentrated. This is what happens in scotland where the SNP won >80% of scottish seats with ~45% of the scottish vote (helped because the opposition is split 4-ways in scotland).

Mostly, the party who gets most seats has also won the popular vote (but get a disproportionate share of seats). This has failed 3 times in the last century in close elections where the party who lost the popular vote still got a small majority because they got lucky with how the votes were spread.

In short: this is how the system is meant to work: there are arguments for changing it but there are also arguments that it has advantages. And it won't change unless a party wins a majority under the current system and decides to change it.

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