Stephanie Peacock, the MP for Barnsley East, has quit from Labour‘s front bench saying she felt in 'all good conscience' she had to vote against any form of second Brexit referendum.
Ms Peacock resigned as a Labour whip, saying she wanted to ‘respect the result of the 2016 vote’ and her constituents would expect her to ‘honour that promise’.
The party's MPs had been told to abstain, but a total of 24 backed the call to delay Brexit in order to hold a second referendum, with 17 opposing it.
Labour leader Jeremy Corbyn's office said it was a matter for the whips to decide what action, if any, they would face.
The amendment, pushed by The Independent Group's Sarah Wollaston, was overwhelmingly defeated by 334 votes to 85 as the bulk of the Labour Party stayed away from the voting lobbies.
In her resignation letter, Ms Peacock told Mr Corbyn: "I was elected on the Labour manifesto that pledged to respect the result of the 2016 EU referendum. The people of Barnsley elected me to honour that promise and that is what I did tonight.
"I felt in all good conscience I had to vote tonight to clearly rule out any form of second referendum.
"I believe the people spoke in 2016 and we need to enact their decision."