Britain will suffer an “economic shock” if the European Union refuses to sign a free trade deal after Brexit, a Government minister has admitted for the first time.

Lord Price, a minister in the International Trade department and the former managing director of Waitrose, admitted that the Government must “ensure” that British and European businesses “don’t find themselves staring at a cliff face created by a gap in our trading relationship”.

It came as Boris Johnson, the Foreign Secretary, continued to heap pressure on Theresa May over Brexit, urging her not to let the negotiations “drag on”.

He said that the Government should “get on” with triggering Article 50 – the formal process for leaving the EU – despite being rebuked by Mrs May just days ago for saying the Prime Minister should do it “early” next year.

Mr Johnson also accused British businesses they must stop “mainlining” immigration “like a drug” as Britain prepares to leave the EU.

Lord Price’s comments, made in a speech last week in Hungary, are in stark contrast to those of other senior Tories who insist that the UK could sever all ties with the EU and still flourish.

Both David Davis, the Brexit secretary, and Liam Fox, Lord Price’s boss in the trade department, have previously suggested that the UK could quit the EU without doing a free trade deal with Brussels.

Experts have claimed that a failure to secure a free trade deal with Europe could cost Britain billions of pounds a year.

Lord Price said: “And as I look to the future, my role will be as much about negotiating free trade deals, as it will be about making the case for free trade.

“I want to ensure that when we leave the EU, British and European businesses don’t find themselves staring at a cliff face created by a gap in our trading relationship.

“Such an event would cause an economic shock that the EU and UK don’t need.”

Mrs May has warned her ministers not to reveal any information about Britain’s plans ahead of the start of the Brexit negotiations.

She has repeatedly said that she does not want to “put Britain’s cards on the table” before the process has even started.

Speaking to the BBC’s Andrew Marr programme, Mr Johnson indicated that he would like to see the Brexit negotiations – which can take up to two years – wrapped up before the next set of elections to the European Parliament in May 2019.

“There is obviously Euro elections coming down the track,” he said.

“I think people will be wondering whether we want to be sending a fresh batch of UK Euro MPs to that institution which, after all, we are going to be leaving. So let’s get on with it.”

Attacking businesses over their reliance on foreign workers, Mr Johnson said that unlimited immigration from Europe for the past 25 years had left firms addicted to cheap labour from abroad.

He said: “For 25 years, UK business and industry has been mainlining immigration like some kind of drug without actually investing enough or caring enough about the skills and the training of young people in our country.

“That’s what Theresa May and the new government want to focus on.”