Lord Mandelson has accused the Leave campaign of “hoisting the white flag” over its campaign after failing to demonstrate how Britain would boost trade following an Out vote.

The Labour peer said the Brexiters were now using a “UKIP-lite” argument focussed on immigration.

Michael Gove, one of the Conservative ministers campaigning to leave the bloc, wrote in the Times today but omitted any response to Barack Obama’s warnings over future Britain-US trade deals and instead tried to switch the debate to migration and EU bureaucracy.

Vote Leave communications director Paul Stephenson had previously said they would “focus mainly on economic arguments” leaving concerns about immigration to the “UKIP-centred group”.

Gove’s article came as Iain Duncan Smith admitted to the BBC it would be a “nightmare” to negotiate trade deals with 27 different countries.

Mandelson said the Leave campaign is in “chaos” over the economic arguments to remain in the EU.

“This was the week when Vote Leave hoisted the white flag on arguments around the economy.

“First the Treasury then Barack Obama demolished their flimsy arguments about trade and prosperity and so they have turned instead to their default nationalist territory of immigration.

“Iain Duncan Smith hammered another nail into their economic coffin when he admitted this morning that it would be a ‘nightmare’ to negotiate with 27 other EU countries in the event of leaving the EU and ‘nobody’ knows how long it would take.

“Vote Leave are in chaos on the economy. Why else would you suggest leaving the Single Market in favour of Britain being more like Albania?

“The economy is not something that can be opted into or out of in this debate – it is the future of this country that is at stake. It’s people’s jobs, prices in the shops and the proper funding of public services that are on the ballot paper in June.”

The Leave campaign attracted criticism following Boris Johnson’s comments that Obama’s “part-Kenyan” heritage could have caused an “ancestral dislike of the British empire”. The US President used his visit to the UK last week to add to the EU debate, saying Brexit would result in the UK being “at the back of the queue” for any trade deal with the US.

Mandelson was appointed EU Commissioner under Tony Blair in 2004 and was previously supportive of Britain joining the Euro.