Shadow Welsh Secretary Jo Stevens has resigned from her position in the shadow cabinet.
The Labour MP for Cardiff Central said she will vote against the three-line whip to trigger Article 50.
Jo Stevens has resigned from the shadow cabinet in protest at Jeremy Corbyn's decision to force Labour MPs to back the Article 50 Brexit Bill.
The Labour leader faces a growing rebellion after imposing a three-line whip requiring his MPs to back the Bill allowing Theresa May to trigger Article 50.
Ms Stevens is the first member of Mr Corbyn's top team to resign over the issue.
She follows shadow education minister Tulip Siddiq in quitting, while two whips have indicated they will also rebel and risk being sacked.
Political commentator Gareth Hughes says her resignation comes as 'no surprise'.