British MPs are expected on Wednesday to approve the first stage of a bill empowering Prime Minister Theresa May to start pulling Britain out of the European Union.

British MPs are expected on Wednesday to approve the first stage of a bill empowering Prime Minister Theresa May to start pulling Britain out of the European Union.

The House of Commons will hold its first vote on legislation allowing the government to trigger Article 50 of the EU's Lisbon Treaty, which would begin two years of exit negotiations.

The opposition Labour party has said it will not block the bill and, although dozens of its MPs could rebel, it should easily pass the next debate stage scheduled for next week.

May is under intense pressure to push the bill through quickly, having promised EU leaders that she will trigger Article 50 by the end of March.

The government had sought to exclude parliament, insisting it had the power to trigger Article 50 on its own, but the Supreme Court last week ruled it must consult lawmakers.

The majority of MPs campaigned to stay in the EU ahead of last June's referendum, but during the first day of debate on the bill Tuesday, many said they would, however reluctantly, bow to the result.

The bill could be delayed in the upper House of Lords, where May's Conservative party does not have a majority and where the unelected peers have no fear of a public backlash.

A new survey revealed that MPs who campaigned to leave the EU are relatively united in what they want whereas those who were on the other side of the referendum have more diverse views.

Some 72 percent of "Leavers" prioritise controlling immigration or not paying into the EU budget over retaining access to Europe's single market.

This reflects May's own position.

She has said she wants to end free movement of people from the EU, a demand she acknowledges is incompatible with maintaining membership of the single market.

"Remainers are much more divided over what to prioritise which may well make them less able to shape the debate," said Anand Menon, director of the UK in a Changing Europe research programme.

The vast majority of Leavers (86 percent) also believe Britain will be able to compensate for any loss in trade with the EU through other deals, whereas 71 percent of Remainers believe it cannot.

Ken Clarke, who may be the only Conservative MP to vote against the Brexit bill, echoed this in his speech Tuesday, accusing Leavers of pursuing a fantasy "wonderland".

At just 143 words, the "European Union Notification of Withdrawal Bill" has been tightly drafted, making it difficult to amend either to delay the government's plans or to tie its hands in the talks.

But May's opponents are still trying, and dozens of amendments are scheduled for debate over three days in the House of Commons starting on Monday.

The bill will then move to the Lords for debate from February 20, with the government hoping for their approval by 7 March.