Liberal Democrat election planner Lord Ashdown has delivered a blunt warning that his party may well lose votes to Ukip in the 2015 general election as public trust in the big three parties "crumbles into dust".

In an interview with The Times that may irritate some in his own party, he publicly admitted what many Lib Dems have feared since the creation of the coalition government - that Labour supporters who previously voted for them to keep the Tories out would now turn to Nigel Farage's party.

"We are now a party of government, not a party of protest, and so you've got Ukip occupying that position," he said.

The former Lib Dem leader also suggested that his party had to shoulder some of the blame for voter disengagement, partly as a result of the economic crisis but also because of the wider loss of trust in national institutions including politics, journalism, the NHS and the BBC.

He expressed surprise that there had not been more violent protest on the streets in reaction to the economic crisis - something he would not rule out in the future.

At the core of his comments was a bleak view of how the public viewed national institutions and how that was helping fuel support for groups like Ukip.

His remarks echoed a widespread fear in Westminster and beyond that issues such as the MPs' expenses scandal, phone hacking and crises in the NHS have combined to fatally undermine trust in key institutions and alienate voters to an unprecedented extent.

UK Riots
Paddy Ashdown fears a return to riots

Among those targeted by Ashdown in an interview with the Times newspaper were bankers who "had their fingers in the till", MPs and journalists. But he also hit out at the BBC and NHS.

"The BBC is revealed as an organisation which can't manage its own affairs, misspends public money and seems to have been complicit in aggrandising someone [Jimmy Savile] whose proclivities would be rejected by most people.

"The NHS, we are told, is to be failing right down to the level of doctors. Nurses were angels but some turn out to be witches," he said.

And the consequences were worrying, he said.

"If this is the age of the collapse of beliefs, the dissolution of institutions, then what you're going to find is people who find an appeal in answers that are simplistic.

"You're seeing a shift to Ukip and a shift to Marine Le Pen (French National Front leader). It can be left or right — the loss of confidence in the politics of the centre, of the three major parties, it seems to me is quite strong," he said.

Such disengagement and anger could even erupt into riots, he said.

"I don't predict them and I don't want them - and I don't want to be scaremongering. But there is something very unsettling out there."

"I cannot exclude the possibility that we'll see people who don't believe they can make their point within the political system making their point on the street instead.

"I'm reminded of the terrible line in Larkin, 'England, with a cast of crooks and tarts'. Now I'm not saying that's true. [However] I think all of these add up to a mood of Jacobinism which I think is quite frightening."