French author and economist Thomas Piketty has urged the British public to vote to remain in the European Union, saying that a Brexit would be "political suicide" for the country. Speaking at the Cannes Film Festival, Piketty stated that voting to leave Europe in the 23 June referendum would be disastrous for Britain's economy and would lead to further fracturing of the United Kingdom.

"I think it will be very sad for Europe. I think it will be, you know, even worse for Britain. I think for Britain it would be like a political suicide because after this happens, very likely, the next step will be Scotland will get out of Britain, which will then become a very small country basically.

"So Britain is less than 1% of the world population, 2-3% of world GDP, but that's going to shrink in the future," he said.

Previously, thinktank Open Europe predicted that UK GDP could be anything between 2.2% worse off and 1.6% better off by 2030 if Britain voted to leave the EU.

Piketty is in Cannes to announce that his book, Capital in the 21st Century, is to be turned into a film. The book reached number one on the New York Times bestseller list and has sold nearly three million copies worldwide. It explores how capitalism affects the world.

"I would never before have thought that I would come to Cannes because my book was to become a film, so this is an incredible adventure," Piketty said.

The film will be co-production between New Zealand and France and will be directed by Justin Pemberton.