8 former US Treasury secretaries think a Brexit could open Pandora's box
The intervention from the former Treasury secretaries comes one day before Obama's visit to the UK - the president is expected to warn against Britain leaving the EU during his time in the country.
The letter published in the Times on Wednesday was signed by George P Shultz, W Michael Blumenthal, Robert E Rubin, Lawrence H Summers, Paul H O'Neill, John W Snow, Henry M Paulson Jr and, Timothy F Geithner - a mix of treasury secretaries that have represented both Republican and Democrat administrations going back to Richard Nixon's presidency.
The former secretaries say that during their times as head of the US Treasury, they benefited from a "special relationship" with Britain, and that the collective efforts between the two countries benefited from Britain being inside the EU.
Here's an extract from the letter, the added emphasis is ours.
The special relationship between the United States and Britain has been at the heart of US economic and foreign policy throughout the post-war period. During our times as US treasury secretary, when confronting difficult global challenges, we often looked to Britain as a strong voice and partner. We often found that our collective efforts benefited from having a strong Britain within Europe.
The letter also outlines one of the most common warnings about Britain leaving the EU - that it will be risky for the economy. Specifically, the letter warns that Britain should "not take for granted its global primacy" as a financial centre if it exits the EU.
We also find compelling the argument of the Remain camp that a vote to leave Europe represents a risky bet on the country's economic future. Brexit could call into question London's role as a global financial centre. For many financial institutions, London has served as the financial springboard into Europe. EU membership allows banks based in London to sell their services across Europe without needing multiple regulatory approvals in each country. 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.
The former treasury secretaries also warn that a Brexit would be a "major setback for the European project":
The departure of one of the EU's strongest economies would hit its finances and boost populist anti-EU movements in other countries. Some even fear that opening this Pandora's box could be a major setback to the European project more broadly.
One of the letters signees, Larry Summers, who served as a Treasury secretary under Bill Clinton, made an even bigger warning when he was interviewed by the BBC's Today Programme this morning. He said that a Brexit would be an isolationist move that would "reduce Britain's very positive influence as an ally of the United States."
Vote Leave, the official Leave campaign, are furious at the letter and have accused the government of "soliciting help from across the pond." Downing street denied this and told the BBC that the treasury secretaries initiated the letter themselves.