Mark Littlewood is Director General of the Institute of Economic Affairs.

Though you wouldn’t know it if from watching the BBC, opinion polls suggest that about half of British people want to leave the EU. But, what would we do if we left? If there is a referendum on continued British membership and the “out” camp have no feasible alternative plan there is little doubt that the electorate would vote to remain in.

The IEA’s Brexit competition sought to provide an answer to this question. The winner, Iain Mansfield, who is a 30 year old member of the diplomatic service based at the British embassy in Manila came up with a very important contribution to the debate.

He notes that trade with the rest of the world is now greater than trade with the EU. At the same time, the rest of the EU have a strong incentive to conclude a trade deal with the UK should we leave. So, as far as trade is concerned, Iain, suggests negotiating free trade agreements with a range of countries whilst also becoming part of the European Free Trade Association. Top priorities for a trade deal would be China, Russia and the USA.

There is nothing to gain, the author argues, from going gung ho into negotiations with the EU. Exit and favourable conditions in any trade deals are likely to be eased if we end our contributions to the EU budget gradually and give migrants some continued rights to remain in the UK. But perhaps the biggest benefits would come from the ability of the UK government to have greater control over regulation.

A whole range of regulatory provisions in the field of employment law, agriculture and the environment, financial services and business and commercial law should be reviewed. This would range from not implementing the proposed directive relating to gender quotas on boards to the important, but technical and rarely discussed Prospectus Directive which imposes unreasonable burdens on small businesses seeking to raise equity.

What would be the economic costs and benefits of all this? The author suggests that overall, Brexit would have a negligible impact on the economy. The worst case scenario would suggest a loss of about 2.6 per cent of national income and the best case a gain of 1.1 per cent. However, perhaps Iain is being a bit cautious here. Regulation imposes costs by impeding competition and reducing innovation – these are hidden costs, rarely included in surveys of costs of regulation. And the worst case of no free trade agreement, even with friendly countries such as Canada and countries eager to grow their economies such as China is hardly plausible.

Nevertheless, these figures do indicate that the decision to leave is, perhaps, largely a political decision. The economics are not decisive in the short run – though maybe they will be in the long run if the EU continues down its current path.

So, the IEA Brexit prize has provided a draft blueprint. It is a piece of work which can begin to shape the debate. And I will end with a warning to those politicians who wish to leave the EU: ignore this at your peril. If you wish to leave by a different exit, fair enough. However, merely to campaign to leave without having any real idea of how Britain should develop its policy in the field of trade, regulation and all the areas in which the EU has competence will lead to a victory for those who wish to stay in.