If the U.K. chooses to exit from the European Union, it would be a “disaster” for science and universities in the country, renowned cosmologist Stephen Hawking, along with over 150 members of the Royal Society, warned in a letter to the Times newspaper.

“We now recruit many of our best researchers from continental Europe, including younger ones who have obtained EU grants and have chosen to move with them here. Being able to attract and fund the most talented Europeans assures the future of British science and also encourages the best scientists elsewhere to come here,” the signatories, who include three Nobel laureates, wrote in the letter published Thursday.

“If the U.K. leaves the EU and there is a loss of freedom of movement of scientists between the U.K. and Europe, it will be a disaster for U.K. science and universities,” they added, citing the example of Switzerland, which they said has struggled to attract young talent from the EU because of restrictions to freedom of movement of workers.

“Investment in science is as important for the long-term prosperity and security of the UK as investment in infrastructure projects, farming or manufacturing; and the free movement of scientists is as important for science as free trade is for market economics,” the scientists wrote in the letter.

British citizens are due to vote on June 23 on whether to remain in the 28-member bloc. Although opinion polls have consistently shown that the pro-EU campaign is slightly ahead, in recent months, its lead over the “vote leave” campaign has narrowed.

“For those who advocate leaving, lost jobs and a dented economy might be collateral damage, or a price worth paying. For me, they’re not. They never are,” British Prime Minister David Cameron is expected to say Thursday in a speech outlining the potential costs of voting to leave the bloc. “There’s nothing more important than protecting people’s financial security. That’s why I believe we are better off in.”