Stephen Hawking has said leaving the European Union would be a 'disaster' for science.
He joins 149 other leading scientists in signing a letter leading the charge against Brexit.
Published in The Times, the letter states:
"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.”
All 150 signatories are fellows at Britain's leading science institution, the Royal Society.
In the letter, they cite Switzerland as an example of what could happen to scientific research in the event of Brexit.
"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."
However, proponents of quitting the EU have argued that a severed membership would bare little effect on research as science is a "public good."
"The problem with this argument is that they’ve entirely missed the economic point about science itself: that it’s a public good.
"That means that it doesn’t actually matter who does the science, where it’s done, only that it is done.