ÃÛÑ¿´«Ã½

On Wednesday a YouGov poll for the Times suggested Jeremy Corbyn was leading the race to become the next Labour leader.

The reliability of opinion polls has been questioned since they failed to predict a Conservative majority at this year's general election.

"Obviously we've got a credibility problem," acknowledged Peter Kellner, president of YouGov.

Opinion polls are still relevant, he argued.

"We are the only people that can give some broad idea of the state and mood of the electorate at this moment."

"I'm proud of what we've done," he added.