Britain's membership of the EU boosts the economy by as much as £92bn every year and should not be given up, according to bosses from some of the UK's biggest companies.
The intervention comes amid simmering tensions over Britain's EU membership in Westminster, where the Conservatives have been forced to rush out a draft law setting out plans for an "in/out" referendum to placate restive Tory backbenchers, in the face of fierce Liberal Democrat opposition.
A raft of influential business leaders including Sirs Richard Branson, Roger Carr and Martin Sorrell, have called for the UK to remain in the EU, but push for reforms to make the bloc more competitive.
In a letter to the Independent on Monday, the 19 prominent bosses said a 'Brexit' would lose the UK 37 trade agreements and the "colossal bargaining power" of the 27-nation bloc.
They also trumpeted the benefits of closer integration on trade to include digital, energy, transport and telecoms, arguing that deepening the single market could more than double the economic benefits of EU membership and boost British GDP by a further £110bn. Currently, membership of the bloc brings an extra £31bn to £92bn into the economy, they said.
"The benefits of membership overwhelmingly outweigh the costs, and to suggest otherwise is putting politics before economics," they said.
While "some of the EU's ideas" on bank reforms could damage London's status as a global financial centre, which should be defended, EU membership also presents opportunities for the banking sector, said the signatories, which included Lloyds chairman Win Bischoff.
The letter chimes with a stern warning from CBI chief John Cridland, who on Friday said the political wrangling over an EU referendum poses an “unnecessary distraction” from the real issues affecting our economy, such as growth and jobs.
Elsewhere, Lloyd Blankfein, Goldman Sachs chief executive, has given the euro a vote of confidence, saying that the risks of the single currency breaking have fallen sharply.
"Of course I believe in the euro," he said in an interview with German newspaper Welt am Sonntag.
"The risk that the euro will break apart or that individual members are headed for bankruptcy was substantially higher a year ago."
The US bank boss said the future of the euro project was effectively sealed due to the strong political will of its members.
"Americans have a history of underestimating the political will of the Europeans to see through the successful creation of a United Europe.
"I'm not going to make the same mistake. The political commitment to Europe and the euro is clear."