THERESA May has sought to reassure Scottish Tory MPs that there will be no “trade-off” with Brussels on UK fisheries and that Britain will retake full control of its waters from December 2020.

The Prime Minister’s reassurance to her Conservative colleagues at a 20-minute private meeting in No 10 came as Michael Gove decried the EU for its “intransigence” in not agreeing the UK should take full sovereignty of its waters after Brexit Day in 2019; this will only come at Christmas a year later.

But in a Commons statement the Environment Secretary issued a thinly-veiled threat to the EU27 that if during the 21-month implementation period it harmed UK fishing rights in any way, then there would be “unhappy consequences” for the remaining member states once Britain became an independent coastal nation in charge of its own waters.

After a draft transitional deal was unveiled on Monday, there were claims of betrayal because full control of UK waters would not come in March 2019, as originally promised, but almost two years later.

Scottish Conservative MPs even suggested such was the “iconic” nature of fishing to Scotland that if there were no cast-iron guarantee of taking back full control from December 2020, then they could seek to vote down the final Brexit deal; a Commons defeat on such key legislation would almost certainly trigger the fall of the Government and a general election.

David Mundell, the Scottish Secretary, raised the fisheries issue at the weekly Cabinet, telling colleagues how it was vital to get the right final deal.

Two hours later, Mrs May called in her Tory colleagues to reassure them about the safeguards British officials had won for the year from December 2019; consultation on quotas and Britain’s share would not be reduced.

Fears that UK fishing could be traded-off to achieve a concession from Brussels in another area of the negotiations were allayed, said one MP present.

“People told the Prime Minister about the strength of feeling in our fishing communities and there was a general reassurance that there would not be a trade-off with Brussels over fisheries. She stressed how we would take back full control in December 2020,” he explained.

In the Commons chamber, Mr Gove, whose father was a fish merchant in Aberdeen, said he shared the “disappointment” of the UK’s fishing communities but he urged people to keep their “eyes on the great prize” of becoming an independent coastal nation from December 2020; the first time in more than 40 years.

Holly Lynch for Labour decried the Government’s “chaotic approach” on fisheries and urged the Secretary of State to show “honesty and clarity” about its negotiating position.

Alistair Carmichael for the Liberal Democrats said there was “palpable anger” in Scotland’s fishing communities. He asked: “If the Government can let us down like this on the deal for the transitional period, how do we know they will not do it again when it comes to the final deal?”

Scottish Tory MPs like John Lamont and Douglas Ross said they had felt badly let down by the transitional deal and asked for a reassurance of full control from December 2020.

Mr Gove said the Government would “seek to secure” the opportunities that the Scottish Fishermen’s Federation and other bodies wanted.

Stephen Gethins for the SNP accused the Conservatives of using Scotland’s fishermen as a “bargaining chip” in the EU negotiations while his Nationalist colleague Pete Wishart accused Mr Gove of peddling a “load of codswallop,” declaring: “The Government will never, ever again be trusted by Scottish fishermen.”

The Secretary of State hit back, saying SNP arguments were undermined by the fact the party wanted to give up complete control of UK waters and keep Scotland in the Common Fisheries Policy.

He accused the Nationalists of “damn cheek” in their claim the Tories were trying to blame Brussels for the transitional deal; the SNP, he told MPs, had “raised grievance to an art form”.