Deputy prime minister says he will stay on and may be willing to sign up to David Cameron's pledge on EU referendum

Nick Clegg has acknowledged that the Liberal Democrats may be left with "zilch" MEPs after next week's elections, and hinted that his party may be willing to sign up to David Cameron's pledge to hold an EU referendum in a future coalition.

The deputy prime minister said he hoped the Lib Dems would not lose all their European representatives but that he would not resign if this happened.

The former Lib Dem MP Lembit Opik had suggested he should step down if voters kicked out more than five of the party's MEPs at the European elections. But Clegg dismissed this idea on his LBC radio show, saying he did not need Opik's advice.

"I do intend to carry on as leader, but I'm actually more confident than many of my critics and commentators think I should be. I'm actually more optimistic about our prospects at the next general election than many people suggest," he said.

Earlier, Clegg refused to rule out agreeing to Cameron's demands on an EU referendum in any future coalition. The Conservative leader has made it clear he would not serve as a prime minister if he could not keep his pledge of a poll by the end of 2017.

Clegg told BBC Radio 4's Today programme that he was more prepared to "die in a ditch" for fair taxes than hold out against the prospect of a referendum.

"Are there die-in-the-ditch issues which I've highlighted in the past that frankly I care about even more than this?" he said. "Yes, I think fairer taxes is something that I've long campaigned for in my political life. I think that people no longer paying income tax on the first £10,000 is not woolly. I've been in a coalition where if it wasn't for us, people wouldn't be getting tax cuts for middle and low incomes, and that is something that I care about much more than the precise mechanics of when a referendum is held.

"My disagreement with David Cameron's approach is I think the timing that he's alighted on for the holding of the referendum is all to do with papering over the cracks in his own party over this."

He repeated his insistence that he wanted a referendum if there was any change to European treaties. "I'm not going to satisfy those people who don't think there should be a referendum at all and I'm not going to satisfy those people who think there should be a referendum next Tuesday come hell or high water," he said. "I've always felt you have a referendum when the time is right, when something happens that merits that referendum."