Theresa May could face a Tory rebellion as MPs demand to see her plan for Brexit.
A Labour motion, which will be debated on Wednesday, will say Mrs May "must commit to publishing the Government’s plan for leaving the EU before Article 50 is invoked".
It is claimed up to 40 of May's backbenchers could join Labour.
Mrs May continued to keep her cards close to her chest on a visit to Bahrain, refusing to rule out the UK paying for access to the single market after Brexit and repeating her promise to achieve an "ambitious" deal.
Tory former minister Anna Soubry, who backed the Remain cause in the referendum and is now a prominent supporter of the Open Britain group calling for close links to the EU, said she would support the Labour motion unless the Government produces a compromise amendment.
She said: "The Labour motion on Wednesday calling for parliamentary scrutiny of the Government's Brexit plan is eminently sensible and supportable.
"The best solution would be for the Government to unite all sides of the House by now agreeing to put before Parliament their plan for the upcoming negotiations.
"It would be a vital and welcome step in healing the Brexit divisions that exist, not just in politics, but across the country."
Leading pro-European former Cabinet minister Ken Clarke has said he intends to vote for the Labour motion.
The Prime Minister's official spokeswoman claimed Labour "want to frustrate the will of the people by slowing down the process of leaving and trying to tie the Government's hand in the negotiation".
Shadow Brexit secretary Sir Keir Starmer said: "Labour accept and respect the referendum and we will not frustrate the process of leaving the EU.
"But Parliament and the public need to know the basic terms the Government is seeking to achieve from Brexit. This issue is too important to be left mired in uncertainty any longer."