Stephen Hawking is the latest to come out in favour of remaining in the European Union.

Hawking is among more than 150 fellows of the Royal Society, Britain's leading scientific institution, who have signed a letter warning that any threat to freedom of movement could severely affect research in Britain.

In a letter to the Times, they write: "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.

"If the UK leaves the EU and there is a loss of freedom of movement of scientists between the UK and Europe it will be a disaster for UK science and universities.”

They point to the example of Switzerland, which they claim is failing to attract young talent after voting to restrict migration of workers.

"Switzerland pays into the EU and was a popular destination for young scientists. It now has limited access to EU funds because it voted to restrict the free movement of workers, and is desperately trying to find alternative ways to attract young talent."

The letter was organised by Professor Sir Alan Fersht, a pioneer of protein science, and signed by 70% of Royal Society fellows from Cambridge.

Sir Alan told The Times he had emailed all his university’s Royal Society fellows with the letter because he felt it was important to explain their position.

“There is so much hot air going around, and this is something serious,” he told the newspaper. “It struck a chord.”