Andy Clarke, chief executive of Asda, Marc Bolland, chief executive of Marks & Spencer and Miisa Mink, chairperson of Nordic Bakery, are among the business leaders to sign a letter in The Times today claiming an EU exit, the so-called Brexit, would deter investment in the UK.
Leave campaigners point out two-thirds of FTSE 100 firms, including Tesco and Sainsbury, did not back the letter.
A referendum on whether the UK should stay in the EU will be held on 23 June.
The letter - organised by the Britain Stronger in Europe campaign and Downing Street – said: "Business needs unrestricted access to the European market of 500 million people in order to continue to grow, invest and create jobs. Britain will be strong, safer and better off remaining a member of the EU."