IT'S one of the most complicated political matters of our time as things begin to hot up on the Brexit front.

Today, all 13 Scottish Conservative MPs - including Scotland Secretary David Mundell - signed a joint letter warning the Prime Minister that they could not support a deal which failed to restore "complete control and full sovereignty" over the UK's fishing waters.

Mr Mundell is among the few MPs to have viewed the 400-plus pages of the draft agreement finalised on Tuesday, and his inclusion among the signatories sparked speculation that he may be ready to resign from the Cabinet if he is not satisfied by its contents.

In the letter, the MPs warn: "We could not support an agreement with the EU that would prevent the UK from independently negotiating access and quota shares... We also cannot stay in the Common Fisheries Policy after December 2020."

The emergence of the letter came as Cabinet ministers gathered at 10 Downing Street for their historic 2pm meeting to decide whether to give their approval to the plan.