The Prime Minister has indicated she will not back down to Tory rebels ahead of a potential House of Commons showdown on Wednesday night.
The Government has been warned it risks a humiliating defeat on flagship Brexit legislation if it does not accept the demands of up to 20 Conservative backbenchers.
The group are ready to revolt against ministers by backing an amendment to the EU Withdrawal Bill, which calls for a “meaningful” vote on any Brexit deal.
But, speaking hours before a possible vote, Theresa May rejected an offer to accept the amendment “in the spirit of unity”.
Answering potential Tory rebel Anna Soubry at Prime Minister’s Questions, Mrs May warned the amendment could put at risk an “orderly and smooth exit from the EU”.
She suggested the planned change to the Brexit legislation would bar the Government from preparing to put in place a divorce deal and agreed transition phase until a “very late stage in the proceedings”.
The Prime Minister also repeated her commitment to holding a meaningful vote, with Brexit Secretary David Davis having confirmed the Government’s intention to do so in a written statement to Parliament earlier.
Mr Davis also penned a last-gasp letter to Tory MPs early on Wednesday morning as ministers battle to avoid a defeat.
The Prime Minister told MPs: “We were very clear that we won’t commence any statutory instruments until that meaningful vote has taken place.”
Ms Soubry is among those ready to vote in favour of the amendment, brought by senior Tory backbencher Dominic Grieve, in the absence of a Government concession.
She asked Mrs May: “Nobody wants to be disloyal or to bring about more disunity.
“The Prime Minister says she wants a meaningful vote on Brexit before we leave the EU.
“Even at this last moment, would she be so good as to accept [Mr Grieve’s] amendment seven in the spirit of unity for everybody here and in the country?”
Posting on Twitter after her exchange with the Prime Minister, Ms Soubry suggested Mrs May’s answer had not appeased her.
Mr Grieve’s amendment to the EU Withdrawal Bill is set to be backed by Labour, the SNP and Liberal Democrats.
The former attorney general was defiant ahead of the Commons vote, telling Sky News he is “not a rebel” but that his attempts to change the Government’s mind had become a “dialogue of the deaf”.
Speaking after Prime Minister’s Questions at the beginning of a debate on the EU Withdrawal Bill, Mr Grieve insisted he will not back down.
“This amendment has either got to be accepted… or it will be put to a vote,” he said.
He also hit back at former Tory leader and Brexiteer Iain Duncan Smith, who accused Mr Grieve of “grandstanding” over the bill.
Despite ministers having promised MPs a say on the Brexit deal, many fear the Government will merely offer a “take-it-or-leave it” vote.
Commenting on Mrs May’s indication she will continue to reject Mr Grieve’s amendment, Liberal Democrat Brexit spokesman Tom Brake said: “It is no surprise that Theresa May is running scared and the Government is reluctant to give Parliament a vote on the final deal.
“It is desperate to avoid proper scrutiny and push through whatever it manages to negotiate. In any case, what the Tory rebels are demanding is not nearly enough.
“The people, not just Parliament, need to have a vote on the final deal.”