Labour shadow minister Tulip Siddiq has resigned from her party's frontbench over plans to order MPs to back an Article 50 Bill.
Labour leader Jeremy Corbyn said earlier today that he would impose a "three line whip" on the Bill, meaning all of his MPs would be expected to back the legislation, which will grant Prime Minister Theresa May with the power to launch Brexit talks.
Siddiq, who represents the North London constituency of Hampstead and Kilburn, served as a junior member of Labour's front bench as shadow minister for early years.
However, roughly three quarters of her constituents voted Remain in the EU referendum, and the seat remains a tight three-way marginal.
In her resignation letter, reported by the Guardian, the Labour MPs said: "I have always been clear - I do not represent Westminster in Hampstead and Kilburn, I rerepresent Hampstead and Kilburn in Westminster.
"I feel that the most effective place for me to counter Theresa May's hard Brexit is from the backbenches."
MPs will debate the Article 50 bill for five days before finally voting on 8 February, before Parliament goes in to a brief recess.
After that, scrutiny will move to the House of Lords, with Brexit secretary David Davis hoping to pass legislation "in good time" for May to begin Brexit talks by the end of March.