The Supreme Court ruled on Tuesday that May must give parliament a vote before she can invoke Article 50 of the EU's Lisbon Treaty, with Brexit minister David Davis promising a "straightforward" bill within days.

May said last week Britain would quit the EU's single market when it leaves the union, charting a course for a clean break with the world's largest trading bloc.

Many lawmakers said they wanted to see her Brexit plans laid out in a formal 'white paper', which sets out the government's proposals for future legislation, to facilitate greater scrutiny before a parliamentary vote on triggering Brexit.

"I set out that bold plan for a global Britain last week and I recognize there is an appetite in this house to see that plan set out in a white paper," May, whose government had previously declined to publish such a paper, told parliament on Wednesday.

"I can confirm to the house that our plan will be set out in a white paper."

Later her spokeswoman said the government would publish its Article 50 legislation on Thursday, but did not give any details of the likely timeframe for its progress through parliament.

The Institute for Government, a think tank, has predicted the earliest an Article 50 bill could pass through both houses of parliament is the end of February, but expects that early March is more likely.

Several opposition parties have said they will seek to amend the legislation, but the government has said it still expects to be able to stick to May's timetable of triggering Article 50 by the end of March.

It is not clear whether the white paper will be published and debated before the legislation is voted on. The spokeswoman said only that it would be published "in due course".

While lawmakers hope a white paper will force the government to give more detail on its Brexit plan, there are no rules about what it must include and any such document could simply repeat the contents of May's speech.

"We have set out the government's plan for negotiating our exit from the EU, our 12 objectives, we can expect it to reflect that," May's spokeswoman said.