DAVID Mundell will have “forfeited any last scrap of credibility” if he does not quit over a key aspect on fish- ing in the Brexit political declaration, according to Nicola Sturgeon.

The First Minister was speaking after the draft document on the future United Kingdom and European Union relationship was agreed between the two sides’ negotiators.

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A paragraph from the agreement said: “The parties should establish a new fisheries agreement on inter alia – access to water and quota shares.”

But last week the Scottish Secretary and 12 Scottish Tory MPs threatened an unprecedented rebellion when they signed a letter to the Prime Minister warning they would not support a deal that fails to honour pledges made to the fishing industry to negotiate access and quotas “on an annual basis” and not as part of any wider arrangement.

The letter was seen as a threat by Mundell to resign if the red line on the EU getting access to Scottish waters in exchange for reaching a future trade deal was crossed.

At First Minister’s Questions yesterday Sturgeon seized on the issue, arguing May was lining up Scotland’s fishing sector to be used as a “bargaining chip” in trade talks and accused the UK Government of preparing for “another Tory sell out of Scottish fishermen”.

“The political declaration that has been agreed this morning between the UK Government and the European Commission represents another Tory sell-out of Scottish fishermen. The Scottish fishing industry will be used as a bargaining chip in wider trade talks,” she said.

“I will read from a couple of documents. First, I quote from the letter that Scottish Tory MPs sent to the Prime Minister last week, which said: ‘we must be able to negotiate access and quota shares ... on an annual basis, without any pre-existing arrangement being in force. This means that access and quota shares cannot be included in the Future Economic Partnership.’”

“Paragraph 75 of the agreement that was signed off this morning states: ‘Within the context of the overall economic partnership the parties should establish a new fisheries agreement on access to waters and quota shares’. There is no mention of annual negotiations, which, I happen to know, the UK Government was trying, and has failed, to secure. On David Mundell’s position, I would simply say that his position is a matter for him, but if David Mundell is still in office by the end of today, in the light of the political declaration, he will have forfeited forever any last remaining scrap of principle or credibility that he had.”

Sturgeon was later backed up by the EU deputy chief negotiator for Brexit, Sabine Weyand, who tweeted: “We need an EU-UK fisheries agreement that covers both access to waters and market access.”

Mundell did not stand down and tweeted that he was “not taking lessons on standing up for fisherman from Nicola Sturgeon”.

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But Brexiteer Scottish Tory MP Ross Thomson, pictured above, branded the political declaration “unacceptable”, as he said the UK “must be a normal independent coastal state like Norway”.

He tweeted the political declaration commits UK to “establish a new fisheries agreement on, inter alia, access to waters and quota shares” and added: “This means sovereignty over our waters sacrificed for a trade deal.”

Scottish Fishermen’s Federation chief executive Bertie Armstrong said his organisation will continue to seek assurances from the UK Government “that it will remain steadfast”. He added: “We will not rest until the future arrangements are signed, sealed and delivered and we secure critical control over access to our waters and who catches what stocks, where and when.”

Meanwhile, the Ministry of Defence announced the Royal Navy will be able to provide three times the protection to the UK’s fishing fleet post-Brexit after a decision to axe three ships was reversed. HMS Tyne, Mersey and Severn were in the process of being decommissioned.