The Liberal Democrats would be "absolutely foolish" to move against Nick Clegg after poor local election results and an expected fall in support in the European parliamentary elections, the party's president, Tim Farron, has said.

As the Lib Dems await a difficult night of results in the European elections – with the national share of the vote expected to be announced shortly after midnight – Farron dismissed a campaign to unseat Clegg.

The party president, who is widely seen as a strong candidate from the left to succeed Clegg as leader, spoke out amid reports that 12 Lib Dem MPs were prepared to call for the deputy prime minister to resign. Campaigners on the left, calling themselves LibDems4Change, have also published an open letter calling for Clegg to go.

However, Lord Ashdown of Norton-sub-Hamdon, the former Lib Dem leader, said that replacing the deputy prime minister was the "silliest idea" he had heard in his career as he described Clegg as the best prime minister Britain does not have. Ashdown, who was Clegg's patron, added that the number of signatories for the LibDems4Change letter (225) was dwarfed by the number of people (363) who have liked the Lib Dems Friends of Cake Facebook page.

The former Lib Dem leader told the Sunday Politics on BBC1: "This idea that's been put about by these people who are calling for a leadership election is just about the silliest idea I've heard I think in my political career. It's just not serious politics."

Ashdown praised Clegg for having the courage to speak up in favour of the EU in the European election campaign though he admitted that his qualities were not yet appreciated by voters. He said: "Nick Clegg...[is] a man of courage, of integrity, of decency, he's one of the, I think the best prime minister Britain hasn't got, though that hasn't got through to the electorate yet but in the context of a general election I believe it will. I'm devoted to the man and I believe he can do amazingly well in the general election, further than you think."

Ashdown spoke out after John Pugh and Adrian Sanders became the first two Lib Dem MPs to question publicly whether it was right for Clegg to continue. Pugh told the Sunday Times: "Although I admire enormously Nick's bravery, it does not follow that because the captain should go down with the ship, that the ship has to go down with the captain."

One Lib Dem told the newspaper that Clegg was like a "general on the Somme...sending others over the top while being safely ensconced in Westminster".

The MPs spoke out ahead of a long night for the Lib Dems as the European election results are announced. The party will learn whether it is on course to be beaten by the Green party into fifth place when an exit poll is published at 10pm – when results can be reported after voting ends across the EU.

The national party figures should be announced shortly after midnight. But it may take longer for smaller parties, such as the Lib Dems, to know the overall number of seats they have won under the proportional representation voting system.

The Lib Dems suffered significant defeats in the local elections. They lost Kingston upon Thames council in west London after 12 years, delivering a warning to the local MP and cabinet minister, Ed Davey. And the party was estimated to have secured 13% of the vote in the local elections – a huge fall in its support at the 2010 general election. But opinion polls have suggested the party is on course to win a share of below 10% in the European elections, suggesting it is likely to see a dramatic reduction in the eleven seats it won in 2009.

Clegg was given important backing by Farron. The party president told BBC1's Andrew Marr Show: "At this time it would be absolutely foolish for us as a party to turn in on ourselves. What has separated the Liberal Democrats from the Conservatives these last four years is whilst the Conservatives have been like cats in a sack fighting with each other the Liberal Democrats have stood united. That is what we will continue to do. The major reason is because the Liberal Democrats, unlike the Conservatives, actually consented to the coalition."

Farron admitted that many in the party were hurt but said Clegg would lead the party into the general election. "There will be lots of people bruised by the results.The results have been disappointing. There were lots of people out there who did not deserve to lose. All the same across the country … we have seen the Lib Dems do well. Our job is to build those fortresses," he said.

Farron also said it was right for the Lib Dems to remain in the coalition because they needed to take some credit for the economic recovery. He said the recovery would not have been so strong if the Tories had been in office on their own because they would have cut the deficit even more quickly, thereby sucking greater demand out of the economy.

Farron is understood to be keeping his powder dry until next year. He is being seen as the "wasteland candidate" – the person most likely to pick up the pieces if the Lib Dems suffer a huge defeat in the general election.

Philip Hammond, the Conservative defence secretary, warned the Liberal Democrats against leaving the coalition, suggesting it would damage their credibility.

"It's not for me to say who should lead the Liberal Democrat party, that's their business," he told Sky News's The Murnaghan Programme. "But I would say this: the Liberal Democrats came into coalition with us to do a job … If the Liberal Democrats as a party want to be credible, I would suggest they're not going to enhance their credibility by pulling out of the coalition with the job half done."