Charles Kennedy is set to warn Conservative frontbenchers that he is capable of taking their seats at the general election.

The Liberal Democrat leader continues the next phase of his local election campaign today.

He will visit the Yorkshire constituency of shadow deputy prime minister David Davis - which is a key target for the Lib Dems.

"It's very, very marginal and we are now the clear challengers," said an aide to party leader Charles Kennedy.

"Davis has spent more time on trying to become leader of the Opposition than he has on what really matters."

The shadow deputy prime minister secured a majority of just 1903 in his Haltemprice and Howden constituency in 2001.

The Liberal Democrats believe their current strong showing in the polls will translate into major gains in both May's local elections and in the next general election.

The local elections will prove a key test for Kennedy, who is eager to prove that the party can become a serious rival to the Conservatives.

The party is targeting other top Tories including shadow chancellor Michael Howard, transport spokesman Tim Collins and party chairman Theresa May.

"If I were these people I'd be very afraid. We're working very hard and they're not really upping their game," said the spokesman.

Liberal Democrat strategists believe the party has struck the right note with the public on Iraq.

It also hopes to capitalise on a growing perception that the government is out of touch on a range of issues.

The party hopes that policies such as free personal care for the elderly and tuition fees for students - both of which have been introduced in Scotland - will have particular resonance among voters.

"If you're looking at selling a home to pay for care or your children are facing tuition fees to go to university, these issues are equally upsetting," added the party aide.