DAVID Mundell has been forced to deny that he is a man without principles, after refusing to resign over Theresa May’s draft Brexit agreement.

The Secretary of State for Scotland has been under pressure from members of his own party after a slew of government resignations this morning.

Many of those on the way out have questioned the deal’s ability to protect the integrity of the UK, as it calls for a "deeper” customs arrangements, closer to the single market, for Northern Ireland in the event of a no-deal Brexit.

In his resignation letter, outgoing Brexit secretary Dominic Raab said the “regulatory regime proposed for Northern Ireland presents a very real threat to the integrity of the United Kingdom.”

Esther McVey in her resignation letter said it would threaten the "integrity of the United Kingdom, which as a Unionist is a risk I cannot be party to".

Ex-Northern Ireland minister Shailesh Vara said it would mean the economic and constitutional integrity of the United Kingdom would not be respected And Suella Braverman said it would "break up our precious union.”

But Mundell fired back, saying the resigning ministers were wrong, and describing them as carpetbaggers, a term for politicians who seek to win an election in an area where they have no local connections.

In an interview with ITV Border, Mundell said: "I am not taking lessons for standing up for our United Kingdom from carpet-baggers. Only a couple of years ago Dominic Raab was proposing to introduce a bill of rights into Scotland which would have overwritten the Scottish legal system and devolution.

"So I am not impressed by his later day commitment to the Union. I am sure this is more about maneuvering and leadership.”

He said the “best way of keeping the UK together” was “to ensure we have a deal as we leave the EU that Brexit delivers for Scotland and the rest of the UK”

“That is what I am focused on,” Mundell added. “Not being part of some soap opera of resignations and I am not going to be bounced into resigning by carpetbaggers."

But the veteran Scots Tory MP may have difficulty persuading his own colleagues.

Ross Thomson, the Brexit-backing, Johnson supporting Tory MP for Aberdeen South, sent a WhatsApp message to Mundell asking him to go.

In the message, obtained by BBC Scotland, Thomson said the backstop arrangements "mean a separate regulatory regime in Northern Ireland and that they will be more closely aligned with the EU than the UK".

He added: "We have already seen the SNP leaping on this calling for a differential deal in Scotland.

"This arrangement, I feel, is something no Unionist can support. Given that two members of the cabinet have resigned on the basis that the proposals put at risk our Union I want to urge you in the gentlest and strongest terms to follow suit."

Thomson stressed that he believes Mundell is a "great Secretary of State" who is doing an "incredible job", and said he would "support you in whatever you decide".

During First Minister’s Questions, Nicola Sturgeon asked why Mundell had not stood down, and accused him of betraying his principles. “It is not so long ago that the Secretary of State for Scotland and the leader of the Scottish Conservatives said that, if there were to be separate relationships for the UK and Northern Ireland, they would resign. Where is David Mundell today?” she said.

Scottish Tory interim leader Jackson Carlaw said Davidson and Mundell had spent “the past year fighting for the United Kingdom.”

“They are not going to take any lessons from anyone else—not from any carpetbagger who has come late to the defence of the United Kingdom and certainly not from the First Minister,” he said.

Sturgeon said it was unclear how Mundell could “have any other option but to follow through on the principled commitment that they made.”

“Let us see over the course of today whether they have any principles or whether they have a backbone between them. I suspect that the answer to that will be a resounding no”.