In an interview with the Independent on Sunday, he accused the prime minister of "defending the indefensible".
The deputy prime minister described those pressing for a "No" vote in the referendum on the alternative vote system as a "right-wing clique".
Meanwhile, former Tory leader Lord Howard has said the Yes campaign is getting "desperate".'Lashing out'
In his most outspoken language yet, Mr Clegg said the No campaign was built on "lies, misinformation and deceit".
"This nasty No campaign, I hope, will prove to be the death rattle of a right-wing elite, a right-wing 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, Mr Clegg responded: "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 try to get a majority of people on side."
Mr Clegg contrasted the supporters of AV - including the leaders of the Labour Party, Green Party, Scottish National Party, Plaid Cymru and UK Independence Party - with its opponents.'Reactionary interests'
He said: "The other side, you'd have David Cameron, [British National Party leader] Nick Griffin and whoever leads the Communist Party.Continue reading the main story
At the moment MPs are elected by the first-past-the-post system, where the candidate getting the most votes in a constituency is elected.
On 5 May all registered UK voters will be able to vote Yes or No on whether to change the way MPs are elected to the Alternative Vote system.
Under the Alternative Vote system, voters rank candidates in their constituency in order of preference.
Anyone getting more than 50% of first-preference votes is elected.
If no-one gets 50% of votes, the candidate with the fewest votes is eliminated and their backers' second choices allocated to those remaining.
This process continues until one candidate has at least 50% of all votes in that round."Now that tells you volumes about the very reactionary interests that are defending the indefensible".
Mr Clegg also referred to Mr Cameron's sharing of a campaign platform with Labour former home secretary Lord Reid.
"When Conservatives team up with a man as reactionary and backward-looking as John Reid, you know that the old establishment, the old elite, are just thrashing around," he said.Disputed claims
A source close to Mr Clegg said he was not accusing Mr Cameron himself of lying.
But Energy Secretary Chris Huhne has written to George Osborne accusing him of untruths.
Mr Huhne called on the chancellor to withdraw claims that a change to the voting system would make elections more expensive, which he described as a "completely unfounded charge".
"I explicitly warned you the manner of the AV campaign would be as important as the result in the effects on the coalition. Robust debate is normal in British politics. Persistent resort to falsehoods is not," his letter to the chancellor states.
Lord Howard said the Liberal Democrats, arguing for a new system, were "realising they are losing the main arguments".
Speaking to the Sunday Telegraph, he said: "I do think it is remarkable and disappointing that, as the campaign enters its final stages, the Yes group is spending all its time talking about the internal politics of the campaign.
"They are desperate. I don't take anything for granted and it is important we get our vote out, but every opinion poll now seems to show a bigger margin in favour of No than the last one."
A referendum on 5 May will ask British voters whether they want to switch to the alternative vote, where voters rank candidates in order of preference.
Westminster MPs are currently elected through the first-past-the-post system.
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