Jeremy Corbyn faces a new Brexit rebellion after Labour's shadow cabinet agreed to impose a three-line whip on the MPs to back the Article 50 bill in the House of Commons on Wednesday evening (8 February).
The top team made the controversial decision on Tuesday morning, a Labour source confirmed to IBTimes UK.
The move comes after a string of Labour MPs, including former shadow early years education minister Tulip Siddiq and former shadow Welsh secretary Jo Stevens, quit the party's frontbench in order to vote against the Article 50 bill following its second reading in the Commons.
The draft legislation is needed for the UK government to trigger divorce talks with the EU. The bill will have its third reading in the Commons on Wednesday followed by the vote.
Corbyn has tabled numerous amendments to the draft law, including an anti-tax haven concession.
"Labour's amendments are the real agenda," a spokesperson for the Labour leader said.
"The challenge is for MPs of all parties to ensure the best deal for Britain, and that doesn't mean giving Theresa May a free hand to turn Britain into a bargain basement tax haven."
May and some of her cabinet ministers left the Conservatives' Black and White Ball early on Monday evening to return to the Commons in a bid to block opposition amendments to the Article 50 bill.
Labour's shadow Home Secretary Diane Abbott also made an appearance in Parliament on Monday. The senior Labour MP abstained on the second reading of the bill because she was "too ill" to vote on the draft legislation, according to a source close to Abbott.
The government is hoping to pass the Article 50 bill through parliament by 7 March and trigger Brexit talks on 9 March. But the draft law could be delayed in the House of Lords, where the Liberal Democrats and Labour have more than 300 peers.
May has warned MPs not to "obstruct the will" of the British people by attempting to block the Article 50 bill.
"The message is clear to all: This House has spoken and now is not the time to obstruct the democratically expressed wishes of the British people," she said on Monday.
"It is time to get on with leaving the European Union and building an independent, self-governing, global Britain."