Can the UK Prime Minister immediately withdraw the country from the EU without backing from parliament?

I am not asking if this is legal, or if it is possible to do without committing political suicide. Let us assume that the next Prime Minister might be so zealous about Brexit that they would be willing to end their career (or if found to have acted illegally, be punished). Could they, on day one of their leadership, take a flight to Brussels and announce that the UK withdraws with immediate effect?

The EU has said on many occasions they will not interfere with the internal politics of Britain on this matter. Does this mean they would have to accept this from the PM whether the PM actually had the power to do it?

Edit: originally specified no deal, which was mentioned as not being possible due to the details of the extension. Ad I understand though it would be possible to accept the negotiated deal at any time. Could this be done without parliamentary approval?

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    If memory serves me well there was a question a few weeks back about whether or not the UK could leave the EU outside of the deadlines laid out in the latest extension deal. The answer is no. Commented Jun 24, 2019 at 17:40
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    Are the various statements made at the time of the extension from Theresa May about hoping not to need the full extension misleading? I might need to rephrase the question. I have seen that in the US the president has been unable to act on his more controversial plans due to the system of checks and balances. However all official correspondence I have seen from the UK to the EU was signed by Theresa May alone... with the approval of parliment, but as somebody who wishes to continue as a politician and therefore wouldn't dare go against them. Her replacement might decide it is worth it. Commented Jun 24, 2019 at 17:42
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    There was a joint statement when May got her extension, which basically said (if memory serves me well) that the UK would leave before EU elections if they found a solution by then, would leave before the EU parliament sits if they don't participate in EU elections, else would leave on Oct 31. Anecdotally, it prompted me to ask Andrew Sparrow (The Guardian's Political Live blogger) whether the UK could leave at other points in time should Johnson become PM, and the answer he came up with at the time was no. Commented Jun 24, 2019 at 17:55
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    @Trilarion A lot of things have happened in the last three years that might previously not have been considered realistic scenarios. The current forerunner in the leadership race has demonstrated that he has little scruples when it comes to getting what he wants. I want to put my mind at rest that he does not have the power to get away with this. He has been pretty untouchable over his political career with constant foot in mouth moments doing nothing to dampen his appeal to certain people. Commented Jun 25, 2019 at 19:04
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    @Trilarion I'm not speaking of the deal itself, which the EU has shown no inclination to renegotiate, but the PM's authority to invoke the deal or to attempt to negotiate a different deal or a no-deal departure at a date other than the pending deadline.
    – phoog
    Commented Jun 25, 2019 at 19:06

3 Answers 3


Can the UK Prime Minister immediately withdraw the country from the EU with no deal without backing from parliament?

No, but there is a statutory instrument that the UK will withdraw from the EU on the 31st of October. What that means is that the UK will leave unless there is another extension to that deadline, which will have to be agreed with the EU and will have to pass in the UK parliament.

To avoid another extension, the UK prime minister could pull a trick by proroguing parliament. By ending the parliamentary session, the UK parliament cannot vote for another extension. Seeing that the current extension is already written into UK law, it's binding.

The UK PM cannot withdraw immediately without the support of parliament because of the same reason. Current UK law says that the deadline is 31 October. To change that would require action from parliament.

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    So it is 100% in their power to allow this to happen by suspending parliament no matter what the wishes of parliament or the british people. This whole thing just seems to spit in the face of everything I know about democracy, that one man (I believe all female candidates have been eliminated) can control the entire future of the country in this way with nothing to stop him. Commented Jun 24, 2019 at 17:51
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    Never been a Theresa May fan I admit but throughout all this it seems that she has been trying to do what the country wants, impossible as it may be to work that out. At least one of her likely successors seems to just want to get what he wants and damn the country. Since the public has no say in who will lead us, this is terrifying to me. Commented Jun 24, 2019 at 18:03
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    @ChrisClayton - Didn't the British people vote to leave the EU? As ridiculous a choice as that was, wouldn't doing so be carrying out the wishes of the British people?
    – Obie 2.0
    Commented Jun 24, 2019 at 20:22
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    You are right of course... but if that was all that there was to the matter then why not just leave the day after the result and save 3 years of tearing the country apart? Commented Jun 24, 2019 at 20:24
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    @Abigail you could say that about any political position in a representative democracy. Politicians will always use sound bites or summaries of their ideas. And when in power it will always be a compromise between parties / factions within the same party. In this case, it's just a very drastic position with many consequences which hasn't been worked out sufficiently, but it's not that different otherwise.
    – JJJ
    Commented Jun 24, 2019 at 22:45

Short answer: no.

If the Prime Minister were to attempt such a declaration, it would be taken rather quickly to the UK Supreme Court, as well as the European Court of Justice, who would almost certainly annul such a declaration.

Furthermore, the EU would not accept such a declaration from a UK Prime Minister, as it would be contrary to EU law (which states that the UK leaves on 31 October, or sooner if the Withdrawal Agreement is approved by Parliament).

As the other answer has already indicated, as both UK and EU law currently stand, the Prime Minister can declare the UK's withdrawal on 31 October at 23:00 GMT. Parliament will not need to assent to this, but it is possible for them to change the law to require the Prime Minister to do something else.

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    The conclusion of this answer is correct, but it doesn't seem to take the mechanics of article 50 correctly into account. There is nothing in the treaty that requires or even allows the PM to "declare the UK's withdrawal." Rather, the withdrawal occurs "from the date of entry into force of the withdrawal agreement," or, if there is no agreement, automatically at the deadline, which was originally two years after invocation of article 50 but has now been extended to 31 October.
    – phoog
    Commented Jun 25, 2019 at 2:05
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    Parliament can pass any bill it wants concerning different dates, but the only options to change the deadline are (1) negotiate a withdrawal agreement with a different date, (2) negotiate an extension to the deadline, (3) revoke article 50, or (4) allow the UK to "crash out" (i.e., leave without an agreement) at the deadline.
    – phoog
    Commented Jun 25, 2019 at 2:07
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    @phoog There is a fifth option, but it would need Parliament’s approval. It’s for the UK to unilaterally withdraw from the EU treaties without using the process defined in Article 50. There would obviously be no agreement, nor any prospect of one.
    – Mike Scott
    Commented Jun 25, 2019 at 16:58
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    @MikeScott how would that work?
    – phoog
    Commented Jun 25, 2019 at 17:12
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    @phoog We’d just send the EU a letter saying that we were withdrawing from the EU treaties, effective as of <date>. There would need to be a lot of domestic law to tidy it up legally, but that wouldn’t have any effect on whether we were an EU member in international law.
    – Mike Scott
    Commented Jun 25, 2019 at 18:27

To answer your additional question that was added later, the Prime Minister cannot leave the EU under the negotiated Withdrawal Agreement (or any other withdrawal agreement that they may negotiate) without the House of Commons voting in favour of the agreement. That’s one of the amendments that was made to the EU Withdrawal Act before it was passed. And the Commons has so far voted it down three times. Indeed under Parliamentary rules, as the Speaker has made clear, they can’t even have another vote on it in the current Parliamentary session unless it changes in some way.

Here’s a quotation from the Department for Exiting the European Union’s guidance on the Act:

Subsection (1) provides that the withdrawal agreement may only be ratified if a number of conditions are met. These are as follows:
the negotiated withdrawal agreement and the framework for the future relationship have been approved by a resolution of the House of Commons;

  • This answer would benefit from the quotation of European Union (Withdrawal) Act 2018, 13.1.a
    – Denis
    Commented Jun 25, 2019 at 16:25
  • @Denis Done as suggested.
    – Mike Scott
    Commented Jun 25, 2019 at 17:02

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