Nick Clegg laid bare his anger at David Cameron last night, accusing the Conservative party of peddling lies in the run-up to the referendum on the alternative vote on 5 May.

The deputy prime minister included Cameron in an outspoken attack on his coalition partners, claiming they had run a "nasty" campaign to defeat the campaign for electoral reform.

Clegg added that he hoped the "No to AV" campaign would prove to be the "death rattle" for the "rightwing elite".

He told the Independent on Sunday: "The yes campaign has had to fight a campaign against a headwind of lies, misinformation and deceit, and that's been tough on them. When people lie about counting machines that won't exist, about the rise of extremism under AV that won't happen, about costs that won't arise, we should call that.

"This nasty no campaign, I hope, will prove to be the death rattle of a rightwing elite, a rightwing clique who want to keep things the way they are. That's why they are lashing out."

Asked if he was referring to the prime minister, Clegg said: "Look, I include all those, and of course it includes the Conservative party, who like this nice little racket: they get a job for life and they waft into power and they don't even need to bother to try to get a majority of people on side."

A source close to Clegg insisted that the comments were not a personal attack on Cameron and that the running of the coalition government would be unaffected.

The criticism is seen by some in Westminster as an attempt by the Liberal Democrats to create clear dividing lines between the Lib Dems and the Tories in the run-up to the local elections.

It follows yesterday's public spat between Cameron and Clegg over internships which centred on comments made in an interview in which the prime minister admitted to recently giving work experience to a neighbour's son. Cameron said he was "very relaxed" about the situation and that he would continue to help friends by offering their children internships.

The remarks appeared to contradict a policy unveiled by Clegg earlier this month that seeks to reduce the number of unpaid internships, described by the deputy prime minister as a bar on social mobility.

Yesterday, Clegg admitted he disagreed with Cameron. "I'm not relaxed about this at all," he said. "It just can't be right that plum internships are decided by who you know, not what you know."