A group of former U.S. Treasury secretaries, including Larry Summers and George Shultz, have stepped into the debate over the U.K.'s future in the European Union by calling for a "Europe, with Britain at the core."
In an open letter published in U.K. newspaper The Times on Wednesday, the eight ex-treasury secretaries state "a strong Britain, inside the European Union, remains the best hope in our view for securing Britain's future."
"EU membership allows banks based in London to sell their services across Europe without needing multiple regulatory approvals in each country," write the ex-White House advisers, who have served both under Democratic and Republican presidents.
"A U.K. exit is likely to disrupt and reduce trade flows at least for a while," says the group, which is made up of eight ex-secretaries of the treasury including W. Michael Blumenthal, Robert Rubin, Paul O'Neill, John W. Snow, Henry Paulson and Timothy Geithner, as well as Summers and Schultz.
The influential politicians warn that the uncertainty surrounding a so-called Brexit "already appears to be acting as a drag on investment and market sentiment."
The call follows an open letter by 200 U.K. entrepreneurs published this week by the Financial Times also backing for the U.K. to stay inside Europe.
And President Barack Obama, who is scheduled to arrive Thursday in London, is expected to publicly announce his support for Britain to remain in the EU.
The letter was criticized by the Vote Leave campaign, who told the BBC: "Not content with doing down Britain's economy, No. 10 are now soliciting help from across the pond."
British citizens are set to vote on June 23 on whether Britain should remain or exit the EU.
You can read the original letter here.
