Can a future UK government decide to rejoin the EU without a referendum or do they have to hold one?

  • 3
    I assume you are asking specifically about the UK internal politics side to the question of rejoining. The question from the EU side seems to be answered at Could the UK re-join EU after leaving?.
    – JJJ
    Aug 11, 2021 at 20:19
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    I think if the UK rejoins the EU it would be on the EU terms next time, starting with the UK abandoning the pound and adoption the euro. The UK would never get the same benefits that it once had.
    – Mocas
    Aug 11, 2021 at 20:21
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    @JJJ yes, this is specifically about UK side. But also specifically about the requirement of a referendum.
    – Mocas
    Aug 11, 2021 at 20:26
  • 15
    @Mocas The UK would most likely not get back the concessions Thatcher won, no. But getting them on the Euro might or might not be a EU priority. After all, problems in Euro-using country can occasionally trigger risks for the EU itself, as the Greek crisis has shown. Aug 11, 2021 at 20:44
  • 14
    First of all, the referendum to leave was not even binding. The UK could have left the EU or stayed in the EU, with or without that infamous referendum, or with any other hypothetical result that referendum could have given.
    – vsz
    Aug 12, 2021 at 11:24

3 Answers 3


The UK does not have a documentary constitution. This means that there is no single piece of paper that I can refer to which sets out the details of when referendums are necessary.

Instead the UK constitution is based on statute, tradition and convention. In the case of referendums, there are two traditions, which are somewhat at odds. First there is the long tradition of "Parliamentary Sovereignty". This is the principle that Parliament can pass any act. By this principle, all that is needed to rejoin (from the UK side) is a simple act of Parliament. Secondly there is a more recent tradition (only about 50 years old) that legislation that significantly affects the constitutional state of the UK should be put out to referendum. By this principle, the UK should hold a referendum if the government wanted to rejoin the EU.

In practice, the second tradition would most likely hold. In the event of the Lib Dems or the Greens winning a majority in 2024 (stranger things have happened...), they would have done so on the basis of a manifesto promising a referendum, not on a manifesto promising immediate application for re-entry.

A future government does not have to hold a referendum, but it would so anyway.

  • 23
    I’m going to disagree with this answer. The 2016 referendum was so divisive that there will never be another one on this issue. If the UK rejoins the EU it will be because a party makes that a key part of its manifesto at a general election, and if it wins a majority then that will be a clear enough democratic mandate for rejoining.
    – Mike Scott
    Aug 12, 2021 at 5:14
  • 9
    HIstorical precedent would suggest that you join the EU without a referendum, and then the next PM holds a referendum on it. Aug 12, 2021 at 14:44
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    I thought referendums were rare in the UK, Wiki says there's only been three. Have there only been three questions that significantly affect the constitutional state of the UK since the 70s? Aug 12, 2021 at 15:27
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    @AzorAhai-him- There have only been three UK-wide referendums, but the constitutional status of parts of the country (mostly Scotland and Wales) has been subject of multiple referendums within those areas. Whether that's enough to establish a "tradition" I'm not sure.
    – IMSoP
    Aug 12, 2021 at 15:33
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    @DrMcCleod There were general elections in 2017 and 2019, but not in 2018. I think you meant the 2019 one.
    – Mike Scott
    Aug 12, 2021 at 18:57

At the risk of stating the obvious, I imagine any PM who won a general election based on a campaign pledge to rejoin would have a sufficient mandate to do so from the voters. Remember that the Brexit referendum wasn't binding to start with, though it would have been politically risky to ignore it.

  • 3
    Conceivably a PM could win an election based on a lie ("rejoin - never!"), so this does not fully answer the question (although they probably would not survive long enough politically to make this a realistic scenario). Aug 11, 2021 at 21:29
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    @EikePierstorff What do you mean by "Lie"? That manifesto says to stay out of the EU but they actually join? If so, in that case they wouldn't have a mandate to join.
    – Buh Buh
    Aug 12, 2021 at 16:58
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    @BuhBuh, the question as I understand it is not if there is a "mandate", but if they can do it. I do not think the two things are the same. I am not sure about Westminster, but e.g. in my country politicians are not bound by any mandate voters give them. When they are elected they can, in the confines of the law, do whatever the heck they want. Of course the PM would need a majority in parliament, so the rest of his party would need to be in on the deception (I admit things in Britain might work different, so I'd be happy to be corrected). Aug 12, 2021 at 17:23
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    @EikePierstorff In the UK, all legislation has to pass in the House of Lords, which is not elected, and legislation can be amended multiple times and stalled. But there is a convention that this does not happen if the legislation is implementing a manifesto commitment. While a disingenuous party could propose legislation their manifesto did not even hint at, it would need to get through the Lords. That is certainly not impossible, and I'm sure it's happened. Aug 12, 2021 at 23:03
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    @AndrewLeach That is not correct. See the Parliament Acts 1911 and 1949.
    – JBentley
    Aug 13, 2021 at 10:40

When the UK joined the EC in 1973 there was no referendum. The government of Edward Heath (Conservative) signed the treaty, Parliament passed the European Communities Act 1972 (which gave EC law supremacy over UK law) and that was that.

There was a referendum in 1975 but that was after the event and called by the next government under Harold Wilson (Labour). The Labour government called a referendum partly (or mainly) because it was split on the question of EC membership. Ministers were given freedom to campaign for either side and holding a referendum was a way of taking the sting out of the issue within the Labour Party. It was never suggested that there was any constitutional requirement to hold a referendum.

That said, I think political legitimacy is more than merely following the minimum constitutional requirements and I think the public would expect a referendum if EU membership were to be considered in future and a government which took the UK into the EU without a referendum would probably pay dearly in the next general election (just as the party which advocated a second referendum because they didn't like the result of the 2016 referendum paid dearly in the 2019 general election). But there is no constitutional requirement to hold a referendum before joining or leaving the EU.

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