Tulip Siddiq has reportedly quit Jeremy Corbyn's top team after the Labour leader said he would force his MPs to vote for invoking Article 50 and trigger Brexit talks.
Siddiq, a Remain campaigner who entered parliament in 2015, said she had "no choice but to resign" as shadow early years education minister.
"Leaving the European Union presents enormous uncertainty for my constituents, with most believing that the disadvantages of leaving outweigh any potential beneﬁts," the Hampstead and Kilburn MP warned, in a letter seen by The Guardian.
Siddiq's resignation comes just hours after Corbyn said he would impose a three-line-whip on Labour MPs. Shadow business secretary Clive Lewis had previously opposed triggering Article 50, but he said he would now vote alongside the shadow cabinet.
Labour has tabled a number of 'targeted' amendments to the European Union [Notification of Withdrawal] Bill this evening (26 January), including an anti-tax haven amendment.
"Labour will seek to amend the Article 50 bill to prevent the government using Brexit to turn Britain into a bargain basement tax haven off the coast of Europe. Our country can do much better than that," Corbyn said.
"We respect the will of the British people, but not the will of this Tory government to impose fewer rights at work and worse public services, while the largest corporations pay even less tax.
"Labour will ensure that the British people, through parliament, have genuine accountability and oversight over the Brexit negotiations because no one voted to give May a free hand over our future."
The row is a result of the Supreme Court's landmark ruling on Tuesday, which saw the top judges decide eight to three that MPs and peers should have a vote on invoking Article 50. May plans to trigger the mechanism by the end of March.