TWEEDDALE MP David Mundell has been accused of "flip-flopping over his threat to resign".

Last weekend the Secretary of state for Scotland and Tory leader Ruth Davidson wrote to Theresa May saying they would not support any Brexit deal that introduces different arrangements for Northern Ireland.

They said this would "undermine the integrity" of the UK.

And in the Commons on Wednesday, the shadow secretary of state for Scotland Lesley Laird (Lab) asked for clarification on Mr Mundell's position.

She said: "The secretary of state claims that protecting the integrity of the UK is the most important thing to him. The invisible man in the cabinet even got a few headlines for himself this week by flip-flopping over his threat to resign.

"Sources close to him claimed he would resign but he denied it himself yesterday, so let's be clear – yes or no? If there is a deal that creates a border in the Irish Sea and undermines the union, will the secretary of state resign?"

Mr Mundell replied: "On the issue of a border down the Irish Sea it is not acceptable to me or my Scottish Conservative colleagues."

Ms Laird then claimed the government had "just run out of ideas when it comes to Brexit" as she urged the Peeblesshire MP to "support Labour's suggestion for a customs union".

She said: "If he really wants to protect Scotland's place in the UK and stop a border in the Irish Sea he should back Labour's plan for a customs union, so will he?"

Mr Mundell responded: "What I'm absolutely clear on is whatever kind of Brexit might be achieved the worst possible alternative would be a Labour government for this country."

Sources close to Mr Mundell told the Peeblesshire News this week that he has not threatened to throw in the towel.

One told us: "David has not threatened to resign – as people know he is not the kind of politician to bandy resignation threats or make dramatic gestures like that.

"However, he has argued all along that Brexit must not undermine the economic or constitutional integrity of the UK.

"It is an absolute red line for him. His cabinet colleagues know that and they know what it means."