MPs have repeated their call for the government to publish its plan for Brexit in a formal policy document.
A number of Conservative MPs have joined Labour in asking for a White Paper on the government’s negotiating objectives, arguing it will allow for a fuller debate on Brexit.
It comes after the Supreme Court ruled MPs must vote on whether the government can start the Brexit process.
It is thought a Brexit bill could be introduced as early as Thursday.
More than half a dozen Conservative MPs including some ex-ministers are calling for a Brexit White Paper to be published in the coming days.
The BBC understands they have already met with Conservative Party whips.
Downing Street, while not explicitly ruling out a White Paper, has stressed that Prime Minister Theresa May has already set out her plan for Brexit.
BBC political correspondent Tom Bateman said some who had campaigned to leave the EU feared a White Paper might create another vehicle to frustrate the process.
But he said few believed the Article 50 legislation – the official two-year process for leaving the EU – could be under threat.
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Labour is warning it is prepared to engage in “hand-to-hand combat” in Parliament to ensure the process of leaving the EU is fully scrutinised.
The party says it will not oppose Article 50 but will try to amend the law.
The Scottish government, meanwhile, will set out its official response to the Supreme Court’s landmark ruling on Wednesday.
In the Supreme Court on Tuesday, the 11 justices ruled that the UK government was not legally bound to take the views of the Scottish Parliament and other devolved administrations into account when triggering Article 50.
But amid reports that the Scottish Parliament could hold a vote on the issue anyway, former First Minister Alex Salmond told BBC’s Newsnight if its “reasonable proposals” – which include continued access for Scottish firms to the single market – were not listened to, there could be another independence referendum within two years.
The Supreme Court ruled that the government must seek Parliament’s authorisation, in the form of legislation, before it could notify the EU of its intention to leave.
The BBC’s political editor Laura Kuenssberg said she expected a short bill to be published on Thursday, with a view to it being debated for the first time next week.
Theresa May wants to invoke Article 50 – the formal process for leaving the EU – by the end of March, and is seeking the approval of MPs and peers well before that date.
With nearly all Tory MPs expected to back the government, the bill is likely to pass although Labour is seeking guarantees in a number of areas while a handful of Tory MPs – including former ministers Anna Soubry, Alistair Burt and Nicky Morgan – are pressing for an explicit commitment for an official document setting out the UK’s aims.
Brexit Secretary David Davis said in Parliament on Tuesday that he believed Mrs May’s speech last week – in which she set out plans to leave the single market and customs union – was sufficient, but Tory whips are reported to have met potential rebels on Tuesday to discuss their concerns.
‘Ready to go’
Shadow foreign secretary Emily Thornberry told the BBC’s Newsnight programme that Parliament must “keep its eye” on the government as the negotiations unfolded.
“If Article 50 is going to be triggered we will not get in the way of it but we will try and amend the legislation in order to ensure they keep coming back.
“And if necessary there will be hand-to-hand combat on this. We need to make sure that we get the best deal on behalf of the whole country.”
The Lib Dems want a referendum on the final settlement negotiated by Theresa May, while the SNP says it has 50 amendments “ready to go” and expects to be properly consulted over issues such as trade and customs arrangement on an “equal basis”.
Mr Salmond said different arrangements were being proposed for the likes of Gibraltar and the Channel Islands and sections of UK industry and Scotland needed its own deal.
“Why shouldn’t the prime minister pay attention to the wishes of the Scottish people, the Scottish Parliament and the Scottish government?
“If at the end of the day, if Theresa May is not interested in staying in the single market and respecting the wishes of the Scottish people… if she flings down that gauntlet then I fully expect Nicola Sturgeon to pick it up.”
Read more at BBC.co.uk