Nearly half of the Liberal Democrat party want Nick Clegg to resign as leader before the general election, a survey suggests.

The poll, conducted by the Liberal Democrat Voice website, says the party's membership is split almost 50/50 on whether Clegg should lead the party into the election, due in 2015.

The findings will embolden those in the party who want Clegg to stand aside for someone less closely associated with the Conservatives, although there seems to be very little demand for a leadership challenge any time soon.

Some 47% of respondents told Liberal Democrat Voice that they wanted Clegg to remain as party leader and deputy prime minister into the next election. But 46% said Clegg should abandon the leadership before 2015. Those 46% include 14% of respondents to the poll who said Clegg should resign this year. Another 32% of respondents said he should stand down as party leader "at some point (eg, in 2014) before the next election".

Almost a quarter of respondents – 23% – said they would like Clegg to stand down as party leader at some point before 2015 but to continue as deputy prime minister.

The poll is based on replies from 500 Liberal Democrat Voice readers who participated. The site uses party membership records to ensure that people who participate in its membership surveys are genuine members, and in the past its poll results have closely mirrored party election results.

Clegg has repeatedly said he intends to lead the party into the next election. But last month Vince Cable, the business secretary, fuelled speculation about Clegg being replaced by saying that he would not rule out leading the party himself, and that, at 69, he was not too old.

Stephen Tall, co-editor of Liberal Democrat Voice, said the poll findings would be deeply uncomfortable for Clegg.

"Even three months ago, Nick Clegg's leadership wasn't seriously being questioned by many within the party, with calls for his resignation mostly confined to mavericks such as Lembit Opik. Two factors have, I think, changed the equation," Tall said in a post on his website. "First, the coalition's troubles – from the unravelling of George Osborne's budget to the collapse of Lords reform – means many more Lib Dems are increasingly unhappy about being in alliance with the Tories, even though few reckon there's an immediate alternative. For many, in our party and beyond, Nick Clegg personifies the coalition. And just as party members are now starting to look ahead to post-coalition times, so are folk also starting to think whether life would be any easier for the party without Nick at the helm.…

"Secondly, Nick Clegg is more exposed now than he was in May because of Vince Cable's recent hints that he is limbering up for the leadership. Vince is staggeringly popular within the party, as our surveys show, and he has made no bones about the fact that he sees the coalition as a necessity of the electoral maths, not a natural partnership of like-minded souls."

The Lib Dems received 24% of the vote at the general election, but after they went into coalition their support collapsed and now they regularly poll below 10%.

Clegg is vulnerable because he is seen as one of the few people at the top of the party who is ideologically sympathetic to the Conservatives. Cable is a former Labour party member who makes no secret of being uncomfortable about being in coalition with the Tories.

Two other potential leaders – the party president, Tim Farron, and the deputy leader, Simon Hughes – are also firmly on the left of the party.

A source close to Clegg said the poll was "not representative" and that Clegg would not quit as leader. "Nick has repeatedly made clear that he intends to lead the Liberal Democrats into the next election and beyond," the source said.

"Nick has never flinched when things have been difficult and he's not going to start now. He sees things through and doesn't bail out when the going gets tough."ends