A lifelong Tory who once worked for Margaret Thatcher has said he would consider voting for the Labour party after it announced a significant shift in its stance towards Brexit.

Former Conservative MP and columnist Matthew Parris made the comments after shadow Brexit Secretary Keir Starmer announced Labour backed staying in the single market and customs union during a transition out of the EU and possibly for longer.

Mr Parris said that despite his loyalty to the Tories and his opposition to leader Jeremy Corbyn, he began to think about “the possibility of voting for a party that is brave enough to take this stand.”

The move by Labour creates a clear dividing line with the Tories, who are still committed to leaving both the customs union and single market in March 2019 on the day of Brexit.

Speaking to BBC Radio 4, Mr Parris said: “It really is a dramatic shift.”

He added: “I’m a Conservative. I’ve always voted Conservative. I’ve been a Conservative MP. I have never voted Labour. I have never even contemplated voting Labour.

“But when I read this story, though I won’t vote for Labour while Jeremy Corbyn is leader, I did begin to think about the possibility of voting for a party that is brave enough to take this stand.”

Theresa May has said there will be a “transition period” lasting at least two years after the UK leaves the EU in March 2019 during which time the Government aims to negotiate an interim customs arrangement and to operate from outside the single market albeit with ongoing access, in order to avoid an economic “cliff edge” for businesses.

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But Corbyn’s party is to say it hopes ongoing membership of the single market and the customs union might be possible throughout an interim period and have not ruled out it continuing afterwards.

Sir Keir said: “We will always put jobs and the economy first.

“That means remaining in a form of customs union with the EU is a possible end destination for Labour, but that must be subject to negotiations.