Caroline Flint, a former Labour Europe minister, has confirmed she will defy Jeremy Corbyn and vote with the government in favour of its EU withdrawal Bill this evening.
The Don Valley MP said she was breaking a three-line whip for the first time as part of “respecting the outcome of the referendum” and “respecting what I said to my electors in a general election just a few months ago”.
“I believe Labour’s job is to improve this Bill, not kill it as it begins it’s passage through parliament,” she told BBC Radio 4′s Today.
“It’s important that we get on with the job of making sure we can have as smooth an exit from the EU as possible.
Flint backed the Remain campaign in the referendum, but her constituency voted 68.5% to Leave.
She said: “Whoever was in government would have to have a Bill like this begin its journey and I do believe it’s our job to make sure we can improve this Bill, and it certainly needs improving.
“But if we were to vote this Bill down, if we were to, for some reason get the votes tonight to kill it, it would actually cause huge problems because it would end the session of parliament.”
MPs will vote after midnight on the European Union (Withdrawal) Bill which will undo the 1972 European Communities Act that took the UK into the European Economic Community.
The crucial piece of Brexit legislation will transpose existing EU laws into British law.
Foreign Secretary Boris Johnson said this morning that if opposition parties successfully vote down the Bill it will lead to a “completely chaotic” and “disorderly” start to the Brexit process. “We need to get this great ship launched,” he said.
But Labour has accused ministers of using the Bill to stage a enormous “power-grab” as it hands them greater powers to change laws without parliamentary scrutiny.
The Lib Dems will also join Labour and vote against the legislation tonight.