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Britain could quit the EU well within the two-year time limit laid down by Article 50 of the Lisbon Treaty, Tory ex-ministers have told Theresa May.

They also called for a work permit and cap system to control the number of EU migrants coming to the UK.

Led by Leave campaigner John Redwood, the "Brexit Blueprint" urges a "take it or leave it" attitude to EU trade.

Mrs May, who is due to tackle Brexit at the Tory conference on Sunday, says the right deal may not be the quickest one.

She has already stated that Article 50, the formal mechanism for Britain leaving the EU, will not be triggered this year - but faces calls to clarify the government's demands.

'Make a success of this'

The so-called Blueprint was compiled at a private conference in Oxford's All Souls College earlier this month.

It was convened by former Cabinet minister Mr Redwood with other contributions from former Iain Duncan Smith, Owen Paterson, Peter Lilley and Sir William Cash.

Mr Redwood told the meeting there was no reason why negotiations over the terms of British withdrawal from the EU should take anything like the two-year maximum laid down by Article 50.

"It is in both sides' interest to reach an earlier agreement to reduce business uncertainty," he said.

"If there is a breakdown or no likelihood of agreement, then the UK should withdraw and after the two-year period the UK will be formally out. Trade will revert to World Trade Organization rules."

Image copyright PA Image caption Iain Duncan Smith: Migrants should not be eligible for benefits unless they've lived in the UK for five years

But in an inteview ahead of the Conservative Party conference Mrs May told BBC political editor for Yorkshire and Lincolnshire Tim Iredale: "We need to ensure we're getting the right deal for Britain and that means not necessarily the quickest deal.

"So we're taking time to prepare before we formally start the negotiations - what's called this triggering of Article 50... We're going to make a success of this - there are opportunities for us when we leave the EU - but we need to ensure we're taking our time to get the deal right."

The Blueprint says that as Article 50 is triggered, a Bill should be brought forward repealing the 1972 European Communities Act, which gave legal force to the country's membership of the then European Economic Community.

The Bill would convert EU law into British law "and so help ensure a smooth Brexit, minimising disruption to industry and commerce," the Blueprint says. "Subsequently, it would be open to this government and its successors to scrap aspects of EU law not considered in the UK's interests."

It also suggests Britain should either continue tariff-free trade with the bloc post Brexit, but without any obligation to accept free movement of EU citizens - or trade freely under the "relatively light" WTO standard tariffs. "The onus would be on the remaining 27 members of the EU either to accept the current arrangements or insist on a WTO deal," it said.

'Nothing to lose'

While EU migrants should come under the same work permit and cap system as the rest of the world, students, EU tourists and intra-company transfers would be exempt.

Permits would only be issued to lower skilled and lower paid workers if the government judged there were not enough British applicants for such jobs, it said.

Former work and pensions secretary Mr Duncan Smith said migrants should not be eligible for in-work or out-of-work benefits post-Brexit until they have lived in the country for five years, or made National Insurance payments over a four-year period.

Former social security secretary Mr Lilley said outside the EU, the UK could be a leader for free trade worldwide, with the agriculture and manufacturing sectors of developing countries gaining better access to the UK market in return for the UK having better access to markets for their services and high-tech products.

The Brexit Blueprint was published by the Centre for Social Justice and the Legatum Institute. The London-based think-tanks also produced a report suggesting that many supporters of Leave had "nothing to lose" and were disproportionately poorer, older and less well educated than those backing Remain.

Of people living in households earning more than £60,000 a year, 65 per cent backed Remain, the report suggests, but this figure plunged to 38 per cent among those earning less than £20,000 a year.

Earlier this week, International Trade Secretary Liam Fox claimed the UK's trade with the European Union will be "at least as free" after Brexit as it is now.

But Sir David Edward, a former judge at the European Court of Justice, retorted: "Nobody who understands trade law could have possibly have said what he said... When the UK notifies its intent to leave the bloc, the country won't be in the 'driving seat' or be able to 'insist on anything' when negotiating a possible deal with the EU."