Voters will wreak political havoc at the next election if Brexit promises are not fulfilled, a leading “Lexiteer” has warned.

Brendan Chilton, the general secretary of Labour Leave, which campaigned for an EU exit, said “a general feeling that Brexit as people voted for is being undermined” could lead to a realignment of politics.

He told the New Statesman: “I do think if there is a fudge in what people voted for, there will be a political change to come that hasn’t been seen yet. Brexit will be small fry.”

He said history demonstrated that feelings of betrayal were very powerful forces for change: “I don’t think anything angry would happen here, but you could see a fundamental realignment of British politics if people feel betrayed.”

Chilton defined Brexit as control over territorial waters and borders, an end to freedom of movement, no more contributions to the EU budget and an end to the jurisdiction of EU institutions.

“We need to be out of the transitional arrangement by next election,” he said.

He criticised Tory Brexiteers who believed the vote to leave the EU was an endorsement of free market liberalism: "It wasn't. It was a vote in some respects for protectionism and economic patriotism."

Alluding to one of the main Tory voices on free market Brexit, he added: "I spoke to half a million people and they were not Daniel Hannans."

Environment Secretary Michael Gove, a leading Tory Brexiteer, hooked the attention of fishermen in recent weeks after he indicated that other countries would still access EU waters after Brexit.

Meanwhile, the Chancellor Philip Hammond, a Remainer, confirmed rumours that the UK would seek a transitional deal which could last up to three years.

According to a July YouGov poll, 61 per cent of Leave voters said they felt “significant damage to the British economy” was a “price worth paying”, and 39 per cent maintained this even if one of their family members lost a job because of it.