The Lib Dems will play the "honesty card" at the forthcoming general election, the Lib Dem leader Charles Kennedy said on Saturday.

Speaking to his party's spring conference in Torquay, he said Tony Blair and William Hague were "conning" the electorate.

He said they were trying to claims people "could get something for nothing" by telling the public that they can get improved public services without tax rises.

Kennedy launched a scathing attack on William Hague. "Think about that for a moment: a William Hague government. It is almost a contradiction in terms - it would be funny if it wasn't quite so frightening," he said.

But the Lib Dem leader also warned Tony Blair that his reputation would be damaged if he reneged on his promise to deliver a referendum on proportional representation. He said that that possibility of any further Lib/Lab relations would be off unless the prime minister held the promised referendum.

"I think it would be damaging for Tony Blair's political credibility,'' Kennedy said on BBC's Radio Five Live. "I think it would be damaging for trust in politicians as a whole and I also think it would be damaging to the Labour Party."

He set out what he described as a "laid back style" of party leadership. "For me personally as much as politically, what you see is what you get. One of the reasons I'm really looking forward to this election is that it gives me a personal opportunity to speak directly to the country, about the sort of person I am, what kind of people we are.

"Some people even accuse me of being laid back - well I am laid back and the reason I'm temperamentally like that is because I'm tolerant and because I'm a liberal. And I'm proud of that."

He has also denied that the Lib Dems are guilty of conning the public, saying that his party's record in coalition in Scotland and Wales gave a clear sign of how the Lib Dems would run the country should they win the general election.

"Where we have got into power in Scotland and Wales we have pursued this kind of agenda," he told Sky television.

Kennedy also defended his own record, rejecting criticism of his style of leadership. "You have to go through an election campaign before the public get to know you a bit better. That will come in the next few months. I am in this for a marathon, not a sprint," he said.