Parliamentary rules will prevent Theresa May bulldozing her Brexit deal through by staging multiple repeat votes until the Commons surrenders, MPs believe.

The tactic – increasingly seen as the prime minister’s only hope of rescuing her unpopular agreement – is explicitly barred by procedures to stop the government bullying the legislature, they say.

Even if Ms May tries to evade the rules by changing a few words of the motion put before MPs, it would be ruled out of order if it is “the same, in substance, as a question that has been decided”, the rules say.

The crucial hurdle emerged after the prime minister refused several times to rule out bringing back the vote “again and again and again” if, as expected, she loses heavily next week.

With the Commons deadlocked on what should happen next, she is expected to use the looming threat of a no-deal Brexit, now just 81 days away, to pile pressure on MPs to back down.

Asked, by the BBC’s Andrew Marr, if she would “bring it back” after a defeat for her deal, Ms May said only: “I am working on getting this vote through parliament.

“It is for those who oppose the deal to say what the alternative is and, so far, nobody has put forward an alternative that delivers on all those issues and, crucially, delivers on the referendum result.”

But Chuka Umunna, a Labour MP campaigning for a Final Say referendum on the Brexit outcome, said the words of Erskine May, the parliamentary “bible”, were crystal clear.

“I’ve consulted with the clerks of the House of Commons on this,” he told Sky News. “You cannot simply bring the same motion again and again and again – you cannot do that.

“And – even if you sought to bring a different motion through changing one word – if, in substance, it’s the same thing, under the rules of the House of Commons you can’t keep bringing it.”

A second Labour MP, Chris Bryant, echoed the view, saying: “It has been convention for centuries that the House can only resolve a matter once in any session.

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“It’s an important means of preventing government from bullying the Commons. So an identical, or near identical, motion should be out of order.”

The warning came as the prime minister dismissed speculation that she will pull the “meaningful vote” for a second time, because of the scale of the opposition, saying: “We will be holding the vote.”

MPs will resume debating the withdrawal agreement on Wednesday, with the vote expected on 15 or 16 January. Ms May said it would be “that sort of timing”.

Strikingly, during the interview, Ms May appeared unable to point to any progress in persuading the EU to give ground on the Irish border backstop – still the key controversy.

She said she was still seeking “further assurances from the EU”, but made no mention of securing a “legally binding” power for the UK to break free of the backstop, as she promised Tory MPs last month.

The continued impasse points to a big defeat next week, which would plunge the UK into “uncharted territory”, the prime minister conceded.

Both Labour and the Democratic Unionist Party (DUP) seized on the apparent failure to achieve a breakthrough since the vote was pulled three weeks ago.

Nigel Dodds, the DUP’s deputy leader, said: “A number of commitments and promises were made when the meaningful vote was pulled. So far, the fundamental problems that make this a bad deal appear not to have changed.”

And Jon Trickett, Labour’s cabinet office spokesman, said: “Essentially, nothing has changed. The prime minister’s promise to go back to Brussels to renegotiate was a cynical attempt to further delay the vote on her botched deal.”

On repeat votes, Erskine May says: “A motion or an amendment which is the same, in substance, as a question which has been decided during a session may not be brought forward again during that same session.”

It says a decision on whether “verbal alterations” amount to real changes are “a matter for the judgment of the chair [the Speaker, John Bercow]”.

Crucially, Mr Bercow has sought to build a reputation as a champion of backbenchers against over-mighty ministers and has sided with the Commons in most disputes.

If the deal is thrown out, Labour will push for a no-confidence vote, to force a general election – but this is also expected to fail, with no sign of Tory or DUP support.

Large numbers of Labour MPs, and the other opposition parties, will then push for a Final Say referendum on whether to halt Brexit, but Jeremy Corbyn is opposed.

In that vacuum, with parliament unable to agree on any outcome, Ms May will hope the ticking clock counting down to a no-deal Brexit, on March 29, will force MPs to back her deal eventually.

Before that, on Tuesday, Tory and Labour MPs will join forces to block the UK crashing out of the EU without a deal, in the first of many ambushes to put parliament in control.