Sir Richard Branson has teamed up with top businessmen to caution David Cameron his plans to renegotiate the UK's relationship with the EU could harm Britain's economy.
Their warning comes ahead of a much-trailed speech from the PM, expected later this January, on Britain's position in Europe.
The letter, published in the FT, has been signed by PR maestro Roland Rudd, BT chairman Sir Michael Rake, WPP CEO Sir Martin Sorrell, and president of the CBI Sir Roger Carr.
Branson cautioned Cameron over his plans to renegotiate the UK's relationship with the EU
While the leading businessman urge EU reform, they caution against calling for a "wholesale renegotiation of our EU membership", a move they say would "almost certainly be rejected."
"The US is keen to see a strong UK in a strong Europe, fearing a weaker Britain on the sidelines of a more protectionist EU," they add.
The letter comes a week after Sir Richard wrote a blog saying exiting the EU could be a disaster for British business.
"The UK must not become a peripheral country on the edge of Europe," he cautioned.
"This will be damaging to long-term prospects of British business and also in the country's ability to attract new international companies to set up and employ people in the country."
Speaking during PMQs on Wednesday, Cameron said changes in Britain's relationship with the EU "would be good for Britain and good for Europe and I think because of the changes in eurozone which is driving a lot of change in the European Union there's every opportunity to achieve that settlement and seek consent for it."
Commenting at the time, David Miliband said: "The tragedy of government rhetoric over the last two years is that it has demonised the status quo in Europe, without advancing an alternative.
"The fantasy island occupied by Boris Johnson of a club that is all single market and no social, environmental, or judicial cooperation doesn’t exist."