David Cameron urged to call early referendum on EU membership

The leader of the main campaign for Britain to stay in the European Union has urged David Cameron to call an early referendum on the UK's membership of the 28-nation bloc.

Britain Stronger In Europe chairman Lord Rose asked "why would you want to wait?" if the Prime Minister achieved a deal on his reform demands at February's crunch summit of EU leaders.

The former Marks & Spencer boss sought to highlight the trade benefits of EU membership as he insisted debates over migration should not be allowed to "dominate" the upcoming contest.

He released analysis suggesting the EU is worth an average of £670,000 in extra trade for each business that exports or imports goods within the bloc.

The former Marks & Spencer boss acknowledged the EU was "imperfect" but argued that its benefits to the UK outweigh its costs by a factor of 10 to one and warned voters that Britain faces "uncertainty" over its future if it leaves.

Lord Rose's warning came as pro-Brexit group Vote Leave seized on the findings of a study that claims the single market has had "no discernible benefit" for UK exports and has proved "not far short of a disaster" for Britain.

Research from thinktank Civitas found UK export growth in the single market area was 22.3% lower following the creation of the EU in 1993 than it would have been had it continued at its trend rate during the common market years of 1973-92.

Vote Leave chief executive Matthew Elliott said: "The unquestioning mantra that the single market has been good for British trade is wrong and should be challenged as this research makes crystal clear."

The Prime Minister will head to Brussels next month to try to finalise renegotiations of Britain's relationship with the EU before putting the deal to the country in a referendum before the end of 2017.

Lord Rose said he hoped Mr Cameron would secure a deal allowing an early referendum - which some observers believe could come as soon as June.

On a tour of the Brompton Bicycles factor in west London, he told the Press Association his campaign would be ready for a June vote.

"We will be ready for any eventuality," he said. "Once we have a deal, whenever that deal might be, let's assume it is in February, why would you want to wait?

"I think there is enough time to get the information out, to get the facts out, to have a healthy debate. Why would you want to wait?"

He said he would be "happy to join forces" with Mr Cameron, who has indicated he will play such a prominent role in selling any new deal he achieves that voters will be "sick of the sight of me".

"I would expect that deal to be sold very hard by the Government once that deal has been done," Lord Rose said.

"I'm very happy to join forces with the Prime Minister in supporting him in what he has done. I think it is a tough negotiation, let's see what we get from that negotiation.

"As we come towards the period of the referendum we will be very happy to join forces."

Although Mr Cameron has repeatedly insisted that he will "rule nothing out" if he fails to secure a deal, Lord Rose said: "I have heard nothing the Prime Minister has said which suggests he would be voting for an exit.

"I'm confident that he will get a deal and, as far as I'm concerned, although I do not think this is a perfect relationship, the UK and EU have always had a slightly combative relationship, but it is a relationship that benefits both sides.

"The Europeans respect our membership, we get a benefit from being in the EU and I am confident that will continue."

Britain Stronger In Europe is highlighting research by the Centre for European Reform that found Britain's goods trade with the EU is 55% higher as a result of its membership.

The "EU effect" was worth around £133 billion to the 200,000 export and import companies in the UK in 2014, it said.

Calling on Eurosceptics to set out their position, Lord Rose said: "Clearly trade is not going to stop if we came out of Europe, that is a fact. What we don't know is how the Europeans will treat us if we say to them on a Friday night 'look, I'm sorry chaps, we're out but by the way can we have the same deal on Monday morning which we had last Friday?'

"Clearly the answer would be 'very unlikely'.

"What we are pushing to get some clarity on at the moment from the No campaign is 'give us a clue as to what the alternative might look like?'

"Frankly we don't know, there is nothing we can recommend at the moment to the electorate which says 'actually the deal you are going to get is better'.

"The uncertainty factor is a very big factor."

Speaking to LBC radio earlier, the Stronger In chairman recognised that migration was "the issue of our time", but added: "I don't want this referendum to be totally dominated by the migrant crisis."