The EU Withdrawal Bill, which formally converts all European Union (EU) legislation into UK law to ensure complete clarity on Brexit day 'March 29, 2019', returns for a line by line scrutiny by lawmakers in what is referred to as the committee stage of the bill.
Embattled Prime Minister Theresa May, already under pressure from all sides of the political divide over embarrassing high-profile exits from the Cabinet of key ministers, faces the prospect of rebellion from within her party by anti-Brexit MPs unhappy with aspects of the legislation.
The debate on the bill, listed for eight days, will take up more than 470 amendments, running into 186 pages, MPs want to see before the bill can be passed into law.
Opposition Labour and rebels from within the Conservative government are preparing to vote together on some of the amendments to inflict defeats on an already embattled May.
Her Brexit minister, David Davis, tried to head off some of that rebellion by offering the Commons a vote on the final Brexit deal.
But his sop failed to win over most MPs, who feel it would be a hollow vote as they would be given a take it or leave it scenario just days before Brexit and demanded that Parliament be given a vote on the final Brexit deal much earlier.
"Parliament will be given time to scrutinise, debate and vote on the final deal we strike with the EU," Davis told the House of Commons yesterday, adding that it was not clear when such a bill would be published.
Labour's shadow Brexit secretary Keir Starmer welcomed the "significant climbdown" but warned that "the devil will be in the detail".
"With less than 24 hours before they had to defend their flawed (EU Withdrawal) bill to Parliament, they have finally backed down," he said.
The Liberal Democrats reiterated their call for the final deal to be put to a referendum while several Tory MPs questioned what would happen if a deal was only agreed at the last minute before the March 29 deadline - a scenario Davis has suggested was conceivable - and MPs could only vote after an exit.
"Today (Tuesday) the misnamed EU Withdrawal Bill came back to Parliament. It is in fact an undemocratic government power grab," said Labour leader Jeremy Corbyn.
"Its return follows weeks of damaging delay. That has only added to the sense of chaotic dithering around the Conservatives' entire approach to Brexit. Nearly 17 months since Britain voted to leave the EU, we are still none the wiser as to what our future relationship with our biggest trading partners is going to look like," he said.
There will be eight hours of debate in the Commons today, including discussion of how to interpret around four decades of EU law in UK law and the status of the European Court of Justice.
A further seven days of debates have been scheduled in the run-up to Parliament's Christmas break next month.
Scottish National Party's foreign affairs spokesperson, Stephen Gethins, said his party had put forward an amendment to the bill that would prevent a "no deal" scenario so that the UK could remain in the EU if negotiations fail.
"We know there is concern across all parties about this Brexit bill, and the government knows it will have to compromise. I call on all parties to back this SNP reset amendment to ensure we have a safety net should negotiations fail," he said.
The first real threat of a government defeat is expected later in the course of the eight-day debate, when MPs take up the so-called "Henry VIII" powers, which give ministers scope to change laws after Brexit.
Pro-EU MPs within the Conservative party are confident of a rebellion by up to 10 MPs, which could mean a major defeat for the government.
The Brexit date of March 29, 2019 is also set to be enshrined in law as part of the withdrawal bill, in a move announced by May last week.
It is another amendment that does not have a unanimous backing of all MPs.