Britain’s special relationship with the US would be significantly damaged if Britain leaves the EU, according to a former US Treasury secretary, who says Brexit would be unfortunate for the British economy, Europe, the US and the world.

In a strongly worded intervention, Larry Summers, who served under president Bill Clinton, said the move would represent the “most isolationist deed in the last century”, inflicting serious damage on the City of London.

He said the US saw the UK as its “bridge” to the EU, and warned that it would become a “less relevant and less significant economy” if it opted for Brexit.

Speaking before Barack Obama’s visit to Britain, during which thepresident is expected to support David Cameron’s battle to stay in the EU, he said: “It would reduce Britain’s very positive influence as an ally of the United States and a strong participant in the G7 and in the G20. It would be a step towards a more closed, more protectionist, less effective and less prosperous global economy.”

Summers is one of eight former US Treasury secretaries, spanning Republican and Democrat presidents from Richard Nixon to Barack Obama, who have written an article warning about the impact of a vote to leave the EU.

“Brexit could call into question London’s role as a global financial centre. While Britain will remain an attractive centre for finance even if Britain exits, it should not take for granted its global primacy when it is no longer the gateway to Europe,” they write in the Times.

The group claims that the US holds a “critical interest” in the outcome of the referendum on 23 June.

Summers told BBC Radio 4’s Today programme that it was up to British voters to make the decision, but said it was right for people to know how the US felt about it. He said there were sharp partisan divisions in the US so it was worth “pondering” that this issue had united Republicans and Democrats.

“Britain would continue to be involved in global affairs but its role without its anchor to Europe would truly be diminished,” he said in the interview.



Summers said he believed the pound would come under pressure and lead to a contraction in the British economy.

He also predicted that the special relationship between the US and Britain would be affected by a decision to leave the EU.

“I don’t want to say that the United States and Britain wouldn’t continue to have the close ties that come from history but I think the special relationship would translate much less into prosperity for both our countries, and I think the special relationship would have much less influence on the broad world,” he said.

“Much would be lost by the kind of split in the west that a British withdrawal would represent.”



The attack drew an immediate response from the former cabinet minister, and leading Brexit advocate, Dr Liam Fox, who said Summers was wrong to suggest that leaving the EU would be an isolationist move. Instead, he argued that the motivation was to separate from a struggling economy and open Britain up to the rest of the world. He said the “old men of Brussels” were still operating under a 1950s model.

Fox also warned President Obama not to intervene in the referendum question. He told the Guardian the US would accept neither having “enforced open borders decided by a foreign power” nor hand budgetary control to unelected bureaucrats.

“The president, is of course, welcome to his view when the US has an open border with Mexico, a supreme court in Toronto and the US budget set by a pan-American committee,” he said. “Then his views might hold greater weight when he urges the European equivalent on the British people.”

Fox had previously organised a letter from 100 MPs to the US ambassador, Matthew Barzun, urging the president not to intervene in the British referendum debate.

Matthew Elliott, chief executive of Vote Leave said: “These US politicians wouldn’t dream of agreeing to give Nafta [the North American Free Trade agreement] £350m a week, or handing power over to Mexican judges over which criminals they can deport or opening up the US border to Mexican migrants. They would have been laughed out the building if they suggested it. So why do they think that we should do the same with the EU?”