David Mundell should quit as Scottish Secretary if he wants to retain a "scrap of principle or credibility", the First Minister has suggested.

Nicola Sturgeon said the text of the draft UK-EU political declaration announced earlier on Thursday was incompatible with pledges given by the Scottish Conservatives on fishing rights.

The draft document, which sketches out Britain and the European Union's post-Brexit relationship, leaves fishing as a "bargaining chip" in future trade talks, Sturgeon claimed.

Mundell and Ruth Davidson previously wrote a letter to the Prime Minister indicating a deal which did not extricate Scottish fishermen from the EU's common fisheries policy (CFP) by the end of the transition period could be a resigning matter for them.

Brexiteer Scottish Tory MP Ross Thomson has already branded the political declaration "unacceptable" with regards to fishing.

The language in the document refers to "a new fisheries agreement... on access to waters and quota shares" to be arranged between the UK and EU in the future.

Questioned on the political declaration by SNP MSP Alasdair Allan during First Minister's Questions, Sturgeon described it as "another Tory sell-out of Scottish fishermen".

She added: "What we see is that the Scottish fishing industry will be used as bargaining chip in wider trade talks."

The First Minister pointed to a demand from Scottish Tory MPs in a letter to May last week that the UK be able to negotiate "access and quota shares on an annual basis without any pre-existing arrangement being in force".

She continued: "There is no mention (in the political declaration) of annual negotiations, which I happen to know the UK Government was trying to secure, and they failed.

"In terms of David Mundell's position... I would simply say this: His position is a matter for him.

"But if David Mundell is still in office by the end of today, in light of this political declaration, he will have forfeited forever any last remaining scrap of principle of credibility that he had."

Responding by tweet, Mundell said: "Not taking lessons on standing up for fisherman (sic) from Nicola Sturgeon who is committed to trapping them in hated CFP."

He added: "The PM has fiercely resisted the efforts of EU States to make an explicit link between access to our waters and access to markets.

"We will negotiate and decide, as an independent coastal state, on access and quota on an annual basis just like Norway and Iceland do now."

The Scottish Secretary also pointed to a statement cautiously welcoming the agreement by the Scottish Fishermen's Federation.

Chief executive Bertie Armstrong said: "The declaration gives the UK the power to assert its position as an independent coastal state with practical sovereignty over our waters and natural resources.

"However we know that several EU nations will not give up their attempts to link access with trade in order to retain absolute rights to fish around our coastline.

"So we will continue to seek assurances from the UK Government that it will remain steadfast.

"We will not rest until the future arrangements are signed, sealed and delivered and we secure this critical control over access to our waters and who catches what stocks, where and when."

But Scottish Conservative MP Ross Thomson said the declaration would mean the UK's sovereignty over its waters "sacrificed for a trade deal".

He tweeted: "The political declaration commits UK to 'establish a new fisheries agreement on, inter alia, access to waters and quota shares'.

"This means sovereignty over our waters sacrificed for a trade deal.

"That is unacceptable. We must be a normal independent coastal state like Norway."

Speaking in the House of Commons on Thursday afternoon, the Prime Minister insisted fishing rights would not be "traded off" in favour of other priorities.