But he said it was "absolutely right" to have held a referendum on the issue, because in the UK "the people are sovereign".

The prime minister admitted it would be a "challenge but not impossible" to bring the Tories back together again in the aftermath of either a Remain or Leave vote, but that he didn't want the campaign to turn into the "Dave versus Boris show", referring to Leave's most-high profile campaigner Boris Johnson.

"I think it’s very competitive out there," he told the audience. "It’s a huge debate, a lot of people making up their mind. I think people really haven’t decided."

Watch the David Cameron town hall event in full: