Tony Blair threatened yesterday to cut housing benefit from nuisance neighbours as he launched a public defence of plans to dock child benefit from parents of teenage tearaways.

The Prime Minister spoke about the highly controversial proposals as he was challenged in the Commons to name any cabinet minister who backed the scheme.

He told Charles Kennedy, the Liberal Democrat leader: "When we have a firm proposal we will put it before people. But as we've said, we are examining this. If you want to oppose it, oppose it.

"We aren't just examining it in relation to child benefit, we're also examining in relation to housing benefit and persistent anti-social behaviour and offending by families in receipt of housing benefit. Most people in this country will support the idea that if people get benefits from the state, they owe some responsibility."

Mr Blair also came under fire from Iain Duncan Smith, the Conservative leader, who condemned the proposals as gimmicks. The row dominated Prime Minister's Question Time as Mr Blair faced MPs on the fifth anniversary of the election that swept him to power.

Mr Blair has had intense criticism, and pointedly lukewarm reactions from Alistair Darling, the Work and Pensions Secretary, and John Prescott, the Deputy Prime Minister, over the proposal to curb benefits in a crackdown on anti-social behaviour.

Mr Duncan Smith said mockingly: "The Deputy Prime Minister rubbished it on Sunday, the Secretary of State responsible for child benefit rubbished it on Monday. So whose idea was it and when will this be brought in?"

Mr Blair said: "We are examining proposals for these and that is because we will look at every measure necessary to bear down on this problem of truancy, of anti-social behaviour, of juvenile offending. If you want to put yourselves opposed to these measures, do so. It will only show how completely out of touch you are with the British public."

Downing Street could name only one cabinet minister, Estelle Morris, Secretary of State for Education, who supported the plan to dock child benefit. But Ms Morris has made clear she would back the idea only as part of a coordinated package of measure.

Asked to name other cabinet members who supported the proposal, the Prime Minister's official spokesman replied that she was "not the only one", but refused to elaborate.

The spokesman said the child benefit move, and the housing benefit penalty, were "two practical proposals aimed at two practical problems".

He said the problem of penalising innocent siblings who are not truanting was "one issue that has to be thought through" but insisted the barrage of criticism had not killed off the plans.

"The Prime Minister doesn't dismiss the issues that have to be addressed," he added. "Equally, he is determined that the issue of truancy should not be swept under the carpet.

"What he does say is, there's an issue here which has to be thought through. If families are receiving financial aid, then they should be encouraged to send their children to school. We are not at the stage yet where we are prepared to publish the details, but we believe in it sufficiently to explore the options.

"What he wants to do is encourage parents to exercise their responsibilities to bring children to school. Where practical he will use whatever tools are available to him to do that."

In a clear hint at government frustration with the failure of magistrates to penalise the parents of truants and the anti-social behaviour of some residents, the Prime Minister's spokesman said the court system's sentencing policy "can sometimes be counterproductive". The aim was to "nip the problems in the bud before they get to court", he said. "What [the Prime Minister] isn't afraid of underlining is the Government's determination. In the case of housing benefit, we are spending something like £11bn of public money to support people who need the benefit, but along with that goes responsibilities on anti-social behaviour."