Two local Liberal Democrat parties have called on Nick Clegg to quit, as part of a growing grass-roots campaign to oust the Lib Dem leader.

Ribble Valley and Nottingham Lib Dems are the first local parties to vote for a new national leadership election to be held.

As he set out his manifesto plans for the next general election at a press conference in Westminster this morning, Clegg told Politics.co.uk he had "unanimous" support from his MPs.

"We talked about it in a two and a half hour meeting of the parliamentary party last week and yes of course there were a range of opinions but at the end there was unanimous support from all of the MPs at that meeting for my continued leadership," he said.

Under party rules, an election must be called if 75 local parties vote in favour.

The exact scale of the rebellion is not clear, with most votes likely to take place in private.

However, at least three other local parties have also held votes on his leadership, with more thought to be taking place.

In Cambridge, members narrowly voted in favour of retaining Clegg, as they did in both Southwark and Salisbury.

Other local parties are also thought to be in the process of holding votes on his leadership.

It currently looks unlikely that Clegg's critics will amass enough votes to oust him as leader.

However calls for Clegg to quit could escalate this week after Conservative peer Lord Ashcroft releases a series of new polls into marginal Lib Dem and Conservative seats.

Clegg has defended his leadership on the expectation that the Lib Dems will perform better at the general election in areas where they already retain seats.

Ashcroft's polls could call that defence into question.

The Lib Dem leader looked pale and visibly tired this morning. Commenting on his appearance, Daily Mail columnist Quentin Letts, said that Lib Dem leader looked "melancholy" and like a "spat-out smartie".

Clegg insisted that he still felt "perky" and had the stamina to continue in the job.

He also set out plans for the Lib Dems to commit to ring-fencing education spending in another coalition, so that funding would be protected from "cradle to college".

He insisted the party would not be willing to enter any confidence and supply arrangements with other parties, saying that there was no point in forming a "half-pregnant" coalition.

He also refused to join with the London mayor Boris Johnson in declaring former prime minister Tony Blair "mad", saying that he did not want to get into personal insults.

However, asked about comments from Michael Gove's former adviser Domonic Cummings about his leadership, he replied that Cummings appeared to have "anger management problems".

Clegg's speech follows a turbulent period for both the Lib Dem leader and his opponents.

A plot to oust Clegg, launched by a close ally of the business secretary Vince Cable, was foiled after he was revealed as being behind a series of private constituency polls leaked to the press.

The polls, commissioned by Lib Dem peer Matthew Oakeshott, showed several of the party's biggest hitters set to lose their seats if Clegg remains as leader.