The 16-strong Economists for Free Trade, led by Cardiff University economics Professor Patrick Minford, claimed abolishing barriers such as tariffs could boost the economy by £135 billion a year, giving households a £5,000-a-year boost.
The plan was dismissed by the Open Britain campaign group as “absurd” and a blueprint for “economic suicide”.
But report author Professor Minford 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.
“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.
“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.”
Professor Minford put forward his ideas in the run-up to June 2016’s EU referendum, although he admitted in a column for the Sun: “Over time, if we left the EU, it seems likely that we would mostly eliminate manufacturing, leaving mainly industries such as design, marketing and hi-tech. But this shouldn’t scare us.”