We already have a question about why MPs are required to comply with party whips in general. But I would like to know why is an MP required to comply with a Three Line Whip in particular.

I've just seen a post from MP for Tottenham and former Minister for Higher Education David Lammy on his Facebook account saying that he received a reprimand for not complying with Chief Whip on the division(s) of the European (Notification of Withdrawal) bill.

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"You are required to comply with the Whip in the future"

Why would an MP be required to follow what a Three Line Whip asks of them? or are there special circumstances for doing so?

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    Its not a legal requirement, its a "You REALLY REALLY should do this or else" Feb 20, 2017 at 17:00
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    No, the reprimand can have actual serious consequences. I don't know the details of how it works in the UK, but in the US doing similar things could result in the party leadership sidelining you. For example you wont get put on committees, or you wont get party funding, or if its really bad they might not accept you on their ticket when you run next time. The leadership has a broad range of options to heavily pressure you to follow the party line, but technically they can't force you Feb 20, 2017 at 17:03
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    The strongest sanction that a party can impose on one of their MPs is to expel them from the party. At the next election, the MP would then be running (as an independent, unless they've joined another party) against the official party candidate. Feb 22, 2017 at 11:17
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    @SteveMelnikoff It's probably worth pointing out that expulsion from the party would probably require a decision from the Labour party as a whole via the NCC, whereas whipping is a function of the parliamentary leadership, and these two groups may have differing opinions.
    – origimbo
    Feb 23, 2017 at 17:36
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    @origimbo: that is true - and as a result, party discipline could be undermined. Expulsion from the party is also referred to (and is implemented) as "having the whip withdrawn". Feb 23, 2017 at 17:42

1 Answer 1


The use of "required" here is in the sense of "Do this or else...", not "You have no choice". Wikipedia has a pretty straightforward writeup of what a "Three line whip" means:

In the United Kingdom, there are three categories of whip that are issued on particular business. An express instruction on how to vote could constitute a breach of parliamentary privilege, so the party's wishes are expressed unequivocally but indirectly. These whips are issued to MPs in the form of a letter outlining the parliamentary schedule, with a sentence such as "Your attendance is absolutely essential" next to each debate in which there will be a vote, underlined one, two or three times according to the severity of the whip:

  • A single-line whip is a guide to what the party's policy would indicate, and notification of when the vote is expected to take place; this is non-binding for attendance or voting.
  • A two-line whip, sometimes known as a double-line whip, is an instruction to attend and vote; partially binding for voting, attendance required unless prior permission given by the whip.
  • A three-line whip is a strict instruction to attend and vote, breach of which would normally have serious consequences. Permission not to attend may be given by the whip, but a serious reason is needed. Breach of a three-line whip can lead to expulsion from the parliamentary political group in extreme circumstances and may lead to expulsion from the party. Consequently, three-line whips are generally only issued on key issues, such as votes of confidence and supply. The nature of three-line whips and the potential punishments for revolt vary dramatically among parties and legislatures.

Effectively, a three line whip is an ultimatum: "Show up and vote the party line, or suffer the consequences." No one is ever required to comply with an ultimatum (in politics or in anything else), but if one doesn't, they can expect to suffer the consequences associated with that choice.

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