Speaker John Bercow has thrown the UK’s Brexit plans into further confusion by ruling out another vote on the PM’s deal unless MPs are given a new motion.
In a surprise ruling, he said he would not allow a third “meaningful vote” in the coming days on “substantially the same” motion as MPs rejected last week.
With 11 days to go before the UK is due to leave the EU, ministers have warned of a looming “constitutional crisis”.
The UK is currently due to leave the EU on 29 March.
Theresa May has negotiated the withdrawal deal with the EU but it must also be agreed by MPs.
They have voted against it twice, and the government has been considering a third attempt to get it through Parliament.
Mr Bercow cited a convention dating back to 1604 that a defeated motion could not be brought back in the same form during the course of a parliamentary session.
He said the second vote on the prime minister’s deal last week was “in order” as it was substantially different to the first, but any further votes must pass the “test” he had set out to be allowed.
The BBC’s Laura Kuenssberg said the Speaker’s intervention could have a “massive” impact on the Brexit process.
The prime minister’s official spokesman said Mr Bercow “did not warn us of the contents of the statement or indeed the fact that he was making one”.
Analysis by BBC political correspondent Iain Watson
How can the government get another vote on Theresa May’s deal?
Well, first of all, rules are there to be changed.
If MPs suspend or change the “standing orders” of Parliament, they could get the Brexit deal back on the agenda.
Secondly, the government could change the proposition on offer.
The former Attorney General Dominic Grieve has suggested that something “substantially” different would be to ask Parliament to vote for the deal subject to a referendum.
Or change the Parliament?
If MPs can’t discuss the same thing in the same session of Parliament, why not simply start a new one?
What’s the current state of play?
The prime minister had been expected to bring back a third vote on her Brexit deal this week – a week after MPs rejected the agreement for a second time by 149 votes – and ahead of the EU summit on Thursday.
Last week MPs also backed plans to rule out leaving the EU without a deal, and they voted in favour of an extension to the process.
All 27 EU member states would have to agree to an extension.
Brexit minister Kwasi Kwarteng told MPs on Monday that Mrs May would write to European Council President Donald Tusk to ask for a delay.
If the EU agreed to the request for a new exit date, the government would ask both Houses of Parliament to approve the change, he said.
Mr Kwarteng said the length of the extension would depend on “whether the meaningful vote goes through or not”.
“If we have a deal… we will ask for a short extension,” he said.
“Now if for whatever reason that vote doesn’t happen, or is frustrated or is voted down, we will probably ask for a long extension of the period – and that would be a matter for the EU and for our government to decide.”
European leaders are expected to discuss a UK request to extend the Brexit process and delay the UK’s departure at the summit on Thursday.
What’s been the reaction to the Speaker’s intervention?
Ministers and MPs supportive of Mrs May’s deal expressed anger at the timing of Mr Bercow’s intervention.
Conservative MP James Gray, who plans to vote for the deal after rejecting it twice, said he was “absolutely furious”; while fellow Tory Greg Hands suggested Mr Bercow was the only person in the country who was “accountable to nobody”.
Solicitor General Robert Buckland warned there was now a “constitutional crisis” and suggested the onus was on the EU to come up with “new solutions” to enable MPs to vote on the deal again.
“Frankly we could have done without this but it is something we are going to have to deal with,” he said.
He suggested “there were ways around this” – including potentially cutting short the current session of Parliament to an end, a move which would lead to calls for a general election.
Brexit: what do we know?
- As the law stands, the UK will leave the EU on 29 March – with or without a deal
- For this date to change, the EU would have to agree to an extension to Article 50 – the legal mechanism that sees the UK leaving on 29 March – or the UK government would have to revoke it, stopping the Brexit process
- Last week, MPs voted in favour of an extension – either for up to three months to pass legislation if the PM’s deal got approval from the House or for longer if her deal was rejected – but it was not legally binding
- Theresa May was expected to bring her deal back to the Commons for a third time in the coming days
- Now, Speaker John Bercow has said the deal cannot be brought back for another vote if it remained “substantially the same”
- There’s an EU leaders’ summit on Thursday and Friday this week
Opponents of the PM’s Brexit deal welcomed the Speaker’s ruling.
Conservative former cabinet minister Owen Paterson said it was a “game-changer” and would “concentrate minds” ahead of Thursday’s EU summit.
Sir Bill Cash, chairman of the European Scrutiny Committee, said it seemed to make an “enormous amount of sense” given that the Brexit deal has been defeated twice and there would need to be a “substantial difference” to allow a third vote.
But the SNP’s Westminster leader Ian Blackford suggested there was now a “constitutional crisis” and he suggested the prime minister should “immediately” call a meeting of opposition leaders.
The view from the EU
By BBC Brussels reporter Adam Fleming
The EU’s official position is that they are waiting for Theresa May to come to a summit in Brussels on Thursday with a clear statement about how she plans to proceed, and there definitely won’t be any more negotiations when she gets here.
Unofficially, EU officials wonder if the government can get itself out of this situation, either with Parliamentary wizardry or by coming up with UK-only additions to the package, such as new guarantees about the role of Northern Ireland’s Stormont Assembly in the future.
And could the joint UK/EU decision about an extension to the Brexit process, due to be taken on Thursday, be appended to the deal and then count as something new enough to justify another vote in the Commons?
But explain to diplomats that the solution might be the Queen closing Parliament and re-opening a new session with a speech and their reactions are priceless.