The bill to trigger Article 50 and kick-start Brexit will face its first vote today (Wednesday) after the opening debate yesterday in the House of Commons,
Last week the Supreme Court ruled that Theresa May must seek Parliament's approval before starting Brexit negotiations, and a the European Union (Notification of Withdrawal) Bill was quickly created.
The legislation to give the Prime Minister permission to trigger Article 50 is expected to pass the vote, but there could be trouble on the horizon for the Labour Party.
Labour leader Jeremy Corbyn imposed a three-line whip ordering his MPs to vote in favour of the bill, but a growing revolt from pro-Remain MPs might force him to sack frontbenchers who don't comply with the whip.
Shadow ministers Jo Stevens and Tulip Siddiq quit in protest and other frontbenchers have warned they will oppose it, despite the cost of jobs. Catherine West also said she'd oppose the bill, which threatens her position as a Shadow Foreign Office Minister.
Despite the growing tension, ministers remain confident that Mrs May's deadline for triggering Article 50 will be met.