Kellner (pictured) has been in the role since 2007 and before that he was chairman from 2001 – 2007.

He was previously a journalist and political commentator for many national newspapers including The Sunday Times, Independent and the New Statesman, as well as appearing on TV for BBC Newsnight, BBC election programmes and Channel 4 News.

He wrote the Journalists’ Guide to Opinion Polls for the European Society for Opinion and Marketing Research and is a member of the British Polling Council’s committee on disclosure. He has advised on polls and public opinion to the Bank of England, Foreign Office, Corporation of London, National Westminster Bank plc and Trades Union Congress.

Kellner said: "After fifteen years as chairman and then president of YouGov, the time has come for me to hang up my abacus. Five years ago I told Stephan that I wished to stay on for one more general election and then step down, rather than keep the same role until 2020, when I shall be 73. I shall continue to write and broadcast about politics and elections, and look forward to undertaking new projects, including with YouGov.

"I am proud of having played a role in its expansion from a company of 10 people in one room to one that employs more than 600 people in 20 countries around the world."

Stephan Shakespeare, founder and group CEO of YouGov, said: "It has been a pleasure working with Peter, one of our first employees and a trusted partner for over fifteen great years. Peter has been our voice of politics as the company has grown from a small media start-up to a global market research business."

YouGov's chief scientist, Professor Doug Rivers, will now oversee the methodology, and its London political team will continue to be led by Joe Twyman and Anthony Wells.