The European Union (Notification of Withdrawal) Bill is listed for a two-day debate, with a vote scheduled tomorrow.
May's government was forced to introduce the bill after it lost a historic legal battle in the Supreme Court last week to bypass the MPs and begin the process of exiting the 28-nation economic bloc without a parliamentary vote.
David Davis, minister for exiting the EU, opened the debate in the House of Commons with a clear message to MPs.
"It is not a bill about whether or not the UK should leave the EU, or how it should do so. It is simply about implementing a decision already made, a point of no return already passed. We asked the people of the UK if they wanted to leave the EU; they decided they did," Davis said.
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Speaking at a press conference in Dublin on Monday, May had also said that her "message to people is very clear". "The people of the United Kingdom voted on 23 June last year. They voted in a referendum that was given to them overwhelmingly by Parliament. The people spoke in that vote. The majority voted to leave the European Union. I think it is now the job of the government to put that into practice," she said.
"I hope that when people come to look at the Article 50 Bill they will recognise it is a very simple decision: do they support the will of the British people or not," she added.
vote against the Bill, but Labour leader Jeremy Corbyn's whip to back the bill means the government is expected to win.
A group of May's own Conservative party rebels have also backed down after her assurance of a White Paper to be published on her Brexit plans in coming weeks.
The extent of a rebellion within the Labour party rebellion remains to be seen, with several of Corbyn's MPs - including Indian-origin MP Virendra Sharma - indicating they plan to defy the party whip and vote against the bill.
Two of Corbyn's shadow ministers, Tulip Siddiq and Jo Stevens, had quit the frontbench last week, saying they want to vote against the bill. If the vote goes the government's way, the bill will return to the Commons next week for the committee stage when Opposition parties will try to push through a series of amendments.
According to a report in 'The Times', the UK government wants to pass the legislation in time for May to initiate the Brexit process at a summit of European leaders in early March.
The government has told the House of Lords that it wants the new Brexit Bill approved on March 7.
All 28 heads of government from EU member states will meet on March 9 at the two-day European Council summit in Malta, giving May an opportunity to invoke Article 50 at the meeting.