About 200 business leaders, including heads of about a third of Britain’s 100 largest publicly traded companies, called for the country to vote to stay in the 28-member European Union at the in-out referendum scheduled for Jun. 23. Top bosses of some of the U.K.’s biggest companies, including defense contractor BAE Systems, Shell, and EasyJet, signed a letter published in the Times, Tuesday, backing Cameron’s warning that Brexit would put the economy at risk.

Citing British Prime Minister David Cameron’s success at securing reforms from the EU giving the U.K.  “special status” among the bloc, the letter said: “Business needs unrestricted access to the European market of 500 million people in order to continue to grow, invest and create jobs."

"We believe that leaving the EU would deter investment and threaten jobs. It would put the economy at risk,” it added.

The U.K. struck a deal with the EU in Brussels earlier in February following months of negotiations. The agreement provided for regulatory exemptions for London’s financial sector, extra protection for the British pound and a controversial “emergency brake” facility to freeze work benefits for foreign migrants.

“Britain will be stronger, safer and better off remaining a member of the European Union,” signatories of Tuesday’s pro-EU letter said.

However, Tuesday’s letter was not approved by two of U.K.’s biggest supermarket chains, Tesco and Sainsbury’s, along with Barclays, the country’s biggest bank by assets.

“The referendum on EU membership is a decision for the people of Britain. Whatever that decision is, our focus will continue to be on serving customers,” Tesco reportedly said in a statement.

A spokeswoman for Sainsbury’s told the Guardian that it was an “apolitical organization” and the vote on Europe  was a “matter for the British people.” Other prominent names missing from the letter included four of Cameron’s business advisors, Alison Brittain, Jeff Fairburn, Nigel Lawson and Robert Noel. 

On Monday, the pound fell sharply against the dollar to its lowest since March 2009, after popular London Mayor Boris Johnson said he would campaign for the U.K. to exit the EU.