A hard Brexit would boost the incomes of Britain’s 19 million households by £5,000 a year, according to a group of pro-exit economists, who have urged the UK Government to abolish all trade barriers after leaving the European Union.

The report by the 16-strong Economists for Free Trade, led by Patrick Minford, the Cardiff University economics professor, comes as the UK Government is planning in the next few days to publish five new papers on different aspects of Brexit.

These will include: enforcing rights outside the jurisdiction of the European Court of Justice; maintaining confidentiality to ensure documents exchanged between governments remain protected after Brexit and guaranteeing civil judicial co-operation.

The pro-Brexit economists claimed abolishing barriers such as tariffs could boost the economy by £135 billion a year, which would give households the £5,000 a year windfall.

But the plan was dismissed by Open Britain, which campaigns for closer ties with the EU, as "absurd" and a blueprint for "economic suicide".

Prof Minford, the report’s author, said: "Hard Brexit is good for the UK economically while soft Brexit leaves us as badly off as before. 'Hard' is economically much superior to 'soft'.

"Backers of Soft Brexit say it would preserve jobs but what they really mean is that it would preserve existing jobs by stopping competition from home and abroad.

"As every schoolboy knows and every politician ought to know, this aborting of competition reduces jobs in the long run.”

He added: "Competition increases productivity and so employment because higher wages paid for by higher productivity makes work more attractive. Competition also increases our general welfare because we are producing more."

Commenting on behalf of the Open Britain campaign group for close ties with the EU, Labour MP Alison McGovern said: "All anyone needs to know about this absurd plan is that its own author admits it would 'mostly eliminate manufacturing' in the UK.

"Unilaterally scrapping our tariffs without achieving similar reductions in the tariff rates of other countries would see Britain swamped with imports, leaving our manufacturers and farmers unable to compete.

"The levels of bankruptcy and unemployment, especially in industry and agriculture, would sky-rocket.”

She added: "This is a project of economic suicide, not prosperity. No responsible government would touch this report with a barge pole as a source of ideas for our future trade policy."

Meanwhile, David Davis has warned the EU Union that "with the clock ticking" there is no point in negotiating aspects of Brexit twice in an attempt to push withdrawal talks towards discussions on a future trading relationship.

He resurrected the idea of having parallel talks on the divorce with those on a future trade deal, noting how the latter would help progress on the key Irish border issue.

"It is simply not possible to reach a near final agreement on the border issue until we've begun to talk about how our broader future customs arrangement will work," he said.

But the Liberal Democrats claimed the Secretary of State’s attempt to reopen the issue of parallel talks “reeks of desperation at an approaching economic storm and a cabinet who don't have a clue”.

Their Brexit spokesman, Tom Brake, added: “Constant reports of Cabinet spats show our government cannot even agree a position between themselves, let alone win concessions from EU negotiating teams in our country's best interests."