Speaking at his daily election press conference, the Liberal Democrat leader spent some time deploring the way in which "spin doctors and political mechanics" appeared to be dominating the campaign.
He said he could never remember a time when the issues - of education, the environment, Europe - had been bigger.
But Mr Ashdown added: "This whole thing is now being hidden under a top dressing of political management, sound bites, spin doctors - and the public are not getting to debate the real issues that matter.
"When the thing degenerates down to the kind of personality insults that the Prime Minister used over the weekend, I get very concerned indeed.
"When the Prime Minister says on, for instance, [the BBC television programme Breakfast with] Frost [on Sunday], that he doesn't want to personalise the insults, and then at the same time publishes in the Daily Mail a comment like 'the Labour leader is slithering and squirming', I think that demeans the office of Prime Minister.
He continued: "I think it's the kind of campaign which indicates the total panic of the Conservatives."
Mr Ashdown then attacked Labour, as a party, for repeated policy changes - without in any way personalising it in the way the Prime Minister had done. Labour, he said, had abandoned everything it had believed in, and had performed eight changes on Europe alone, while the Liberal democrats stood where they had always stood.
"We haven't had to abandon everything we believed in," he said.
Mr Ashdown was then asked to explain the difference between Mr Major's attack on Mr Blair, "slithering and squirming", and a speech issued in his name at the weekend, in which he supposedly likened Mr Major to a dodgy second-hand car salesman.
Mr Ashdown said: "I did not use the words, 'dodgy second-hand car salesman'. I know that's what people put on the speech that I gave on Saturday. In fact, I said, 'Let's assume that in deciding how to vote at the next election, you were buying a family car'.
"Then I went through the various procedures; the means to express the way that you might go about making a choice. 'Dodgy second-hand car salesman' is not a phrase I recall that I used in that speech at all.
"Let me put it this way; I think there is a great difference between attack and humour in this campaign, and that is the important point."
Earlier, he said: "Two thousand babies are born in Britain each day.
"My message to the parents of those parents born today is that only the Liberal Democrats will make the difference to those children by giving them a real head start in life.
"High-quality early years education is not only the educational foundation stone for every child.
"It is also the first building block in turning Britain into an education superpower.
"We're going to create a school-leavers' class of 2015," he added, "which competes with the best in the world."Reuse content