Iain Duncan Smith has brushed off poor opinion poll results by insisting the Tories "can win the next general election".

Following last week's Brent East by-election defeat the Conservative leader pledged to mount a "major campaign" against the Liberal Democrats.

And he vowed to take on Tony Blair's "government of liars and incompetents".

In a speech to the Carlton Club on Tuesday night, Duncan Smith said the Conservative Party was in the "best position for 11 years".

He said the Tories were the "largest and fastest growing party of local government".

And he vowed to build on that progress to create "a real lead over Labour" by the next election.

"Already, people are sick and tired of Labour," he said. "The 70 per cent increase in council tax. Sixty new tax rises. Failing schools and hospitals. Rising gun crime. Labour's lies about the war."

And he turned his fire on the Liberal Democrats.

In a sign that the Brent East defeat had rattled Central Office, Duncan Smith said the Lib Dems had been allowed to "get away with murder" by sending different messages to different groups.

"Pretending to Conservative voters that they are a moderate party and a suitable alternative to Labour," he said.

"From Guildford to Hereford, from Newbury to Aberdeenshire, we need to remind voters what Liberal Democrats are saying in seats like Brent.

"In Brent, they campaigned on a platform of anti-Americanism and even higher public spending.

"At their conference this week, they are voting to abolish the monarchy, ban smacking and impose compulsory sex education for seven-year-olds.

"They've moved from weak Left to loony Left. Red Kennedy isn't an alternative to Tony Blair - he's his echo."

"Blair's soft on soft drugs - Kennedy's soft on hard drugs too. He wants higher taxes, weaker asylum rules, fewer burglars in prison and an end to our national currency."

And Duncan Smith said the prime minister was now living on borrowed time.

"Most people have been willing to give Tony Blair the benefit of the doubt. But that has now changed," he said.

"Most people now believe that Labour's policy on the public services - the policy of throwing untold billions at them - is failing and will always fail."