LONDON (AP) — Almost 200 business leaders set out the case Tuesday for Britain to stay in the European Union, warning of a risk to investment and jobs if the country opts to leave the 28-nation bloc in a national vote this June.

In a letter published in The Times, the leaders say business "needs unrestricted access" to the European market in order to grow and invest.

"We believe that leaving the EU would deter investment, threaten jobs and put the economy at risk," the letter said. "Britain will be stronger, safer and better off remaining a member of the EU."

Signatories include CEOs at over a third of the country's biggest businesses. They include Bob Dudley of BP, Royal Dutch Shell's CEO Ben van Beurden and Burberry CEO Christopher Bailey.

The chiefs of Heathrow and Gatwick chiefs also signed.

However, there were some notable absentees, including the bosses of Tesco and Barclays.

The letter was organized with the support of Prime Minister David Cameron's office.

Matthew Elliott, chief executive of the Vote Leave campaign, said the letter provides further evidence that "panic seems to be spreading" at Cameron's office.

"The only way to take back control of our economy to help British businesses to flourish is to Vote Leave," he said.