Theresa May would have to delay Brexit if she gives MPs a vote on her negotiating strategy before triggering the formal process to leave the European Union and they reject it, Nick Clegg has admitted.
The former deputy prime minister is leading a cross-party effort to force the Prime Minister to set out her Brexit plan - including whether she wants the UK to remain in the single market - and then give MPs a vote on it.
Cabinet minister Priti Patel reasserted the Government's position that it will not offer a "running commentary" and likened the negotiations to playing poker, insisting Britain cannot reveal its hand before Article 50 to begin the process of leaving is invoked.
She also warned against "subverting the democratic will" of the public and insisted there will be several votes on the so-called "Great Repeal Bill".
The Bill transposes EU law onto the domestic statute book but will not come before the Commons until after Article 50 is triggered.
Mr Clegg instead wants ministers to spell out in a White Paper-style document whether it sees the UK in or out of the European single market before beginning negotiations.
He denied it is an attempt to delay to the triggering of Article 50 of the Lisbon Treaty, telling BBC One's Andrew Marr Show: "It's not at all.
"It is in an attempt to ensure that as the Government pursues its mandate of pulling us out of the EU they do so in a workable way, a legal way and crucially in a way that doesn't throw the single market baby out with the EU bath water."
He added: "I strongly suspect if the Government comes with a sensible coherent plan for Brexit they will win a majority across the sides of the House of Commons."
However, he admitted that if MPs voted against the Government's Brexit plans, the Prime Minister would be forced to pause going ahead with the official withdrawal process.
"Yes, and by the way that would be a very good thing because I think Theresa May has made already a fundamental tactical error by saying, just to throw red meat to her backbenches, that she's going to trigger Article 50 in March of next year, she's already in doing so lost about a quarter of her negotiating timetable", he said.
"As anybody in Europe will tell you, nothing is going to meaningfully happen until the end of next year until after the German election."
He claimed MPs who campaigned to leave the UK are "in a state of Brenial, they are Breniers because they are denying the mendacity of their original campaign".
If Mr Clegg and his allies, which include former Labour leader Ed Miliband, shadow Brexit Secretary Sir Keir Starmer, and Tories Nick Herbert and Stephen Phillips, get their wish of a fresh Commons debate on whether there should be a pre-Article 50 vote, it could prove awkward for Mrs May.
The PM was forced last week to allow disgruntled Tories to back a Labour motion calling for "proper scrutiny" of her strategy amid the threat of a backbench rebellion.
The debate that followed saw several Tory former ministers express concerns about a potential "hard Brexit" outside the single market.
The Government appears to be favouring such an approach because it insists on full control over immigration, seen as incompatible with membership of the free trade zone.
But Ms Patel said she could not reveal more detail about the plan.
"If I were to sit down and play poker with you this morning, I'm not going to show you my cards before we even start playing the game," she told Marr.
She stressed that debates were happening every day in the Commons and the Government would be held to account by a new Brexit select committee.
"We look at everything that happens in Parliament and obviously the debates that are taking place now and the debates that people are alluding to as well," Ms Patel said.
"We will work with all colleagues.
"This isn't about a them or us mentality whatsoever, we are listening to colleagues, respectfully."