The Lib Dems are promoting their stance on ten policies from hospitals to student fees in a bid to show voters they are the "real alternative" party.
Mr Kennedy says he does not want to fight a negative campaign
The party has taken out three newspaper adverts costing £100,000 in the biggest pre-election push in its history.
Leader Charles Kennedy said he wanted a positive campaign and to stay out of Labour and Tory "mudslinging".
Labour says a Lib Dem vote would only help the Tories win, the Tories say they offer the only real alternative.
Three full-page newspaper advertisements were published on Tuesday in the Daily Mail, Times and the Independent.
The Lib Dems say the move illustrates their confidence and their commitments in the run-up to the general election, widely predicted to be called for 5 May.
In the adverts, the Lib Dems highlight government policies which they oppose, such as the Iraq War, hospital targets, compulsory ID cards and "hidden tax increases", then suggest their own alternatives.
Instead of introducing ID cards, they say they would fund 10,000 more police officers.
Other plans include increasing only one tax - on income above £100,000 a year - and introducing free personal care for the elderly, along with £100 extra a month for over-75s.
And they highlight tuition fees, plans to replace council tax with a local income tax and the war in Iraq.
Setting out the policies, Mr Kennedy said he wanted to promote a "positive agenda" to create more "fairness" in Britain, which he said would mark out his party from Labour and the Tories.
"We are determined...that we are going to fight a campaign which concentrates on real solutions to the real problems people face in Britain every day," he said.
He said the party had taken a risk in staying out of "mudslinging" between Labour and the Tories over the past few weeks, but said they were determined to focus on the big issues.
Former Lib Dem leader in the Lords, Shirley Williams, said she thought voters were fed up with "the endless dogfight in politics".
"I think that is particularly true of women and young voters and we are taking a calculated gamble on the intelligence of the electorate," she said.
But Fraser Kemp, Labour's campaign spokesman, said: "The choice at the next general election will be between going forward with Labour or returning to a failed Tory past.
"Whatever promises they make the one thing you can be sure of is that a vote for the Liberal Democrats would only help Michael Howard into No 10 through the back door."
Conservative Party co-chairman Liam Fox said the Lib Dems would be soft on crime, would increase taxes, oppose controlled immigration and were "in favour of giving away more power to Europe".
"The Conservative Party is the only alternative to Tony Blair's failed government," he said.