Liberal Democrat politicians indicated on Tuesday that they have deep concerns over David Cameron's uncompromising post-riots law-and-order agenda, with the party's home affairs spokeswoman in the Lords telling the Guardian there should be "zero tolerance with zero tolerance".

Lady Hamwee, who led the Lords revolt against Tory plans for elected police commissioners earlier this year, said the pledge by the prime minister of zero tolerance on criminality was taking matters too far. Her comment suggests Cameron will meet stiff resistance when parliament returns in September.

Lib Dem backbenchers went further when contacted by the Guardian and accused their coalition partners of short-termism and kneejerk reactions.

David Ward, MP for Bradford East, described plans to withdraw offenders' benefits as "nuts", and Tessa Munt, the MP for Wells, said the plans were "bonkers, bonkers, bonkers". She said: "Frankly, this all smacks of headline grabbing by Conservatives, not calm, rational policy-making."

The vice-chair of the party's federal policy committee, Evan Harris, said he would table an amendment at the party conference asking members to vote to block Cameron's contemplation of barring individuals suspected of causing social unrest from Twitter and Facebook.

On BBC2's Newsnight, Liberal Democrat home affairs spokesman Tom Brake said: "Clearly there are cases where offenders who have committed very serious crimes should expect very serious sentences and that is what I expect to happen. But there have been some cases where people who have committed petty offences have received sentences which, if they had committed the same offence the day before the riots, they would not have received a sentence of that nature.

"This should be about restorative justice, in other words making people acknowledge the offences they have committed and preferably if the victims want it, actually sit down face to face with the victims so they can hear from the victims the impact they have had, but it should not be about retribution."

These signs of Lib Dem disquiet emerged after the party's leader, Nick Clegg, sought to slow down a fast and furious run of Tory policy suggestions, including plans to evict the families of rioters from council houses and a consultation on halting benefit payments to offenders.

The deputy prime minister instead stressed plans to rehabilitate offenders through the government's work programme, softening the hardline language used 24 hours earlier by the prime minister. He also announced a cross-party inquiry into the causes of the riots after brokering a deal between Cameron and the Labour leader, Ed Miliband.

Clegg appeared to put the brakes on the benefit withdrawal plans, saying they would not be entered into without extensive consideration. He told a press conference in Whitehall: "We are going to take our time to look at this. Of course you need to be proportionate, of course you need to be careful, of course you don't want to create unintended consequences where the taxpayer ends up footing more of the bill or we create more social problems or problems of law and order."

Hamwee warned her party would take a dim view if Cameron pushed ahead with a "zero tolerance" approach. "I am worried," she said. "I think there is something in the 'broken windows' theory of policing – that you can bring down crime by catching things early – but not zero tolerance.

"I also think it is very important not to make policy on the hoof. My instinct is that it would be a great pity if what [the justice secretary] Ken Clarke has been doing – finding a better way of sentencing – was to be undone. If it is, we will be taking a backward, regrettable step."

One senior Lib Dem government figure, who wished to remain anonymous, suggested the party would push to derail Cameron's plans for elected police commissioners. The legislation has not yet been passed and is due for consideration again in the autumn.

The party's welfare spokeswoman, Jenny Willott, echoed deputy leader Simon Hughes's opposition, laid out in the Observer on Sunday, to plans to evict people from council houses.

She said the rehabilitation of people who had rioted required them to have enough money to put a roof over their heads and to eat. "I feel strongly, I don't think we can cut benefits," she said. "I do understand that people feel strongly about this and so instead I think there is something to be said for taking a criminal record and whether someone was involved in the riots into account when considering the allocation of social housing. But what is currently being proposed is counter-productive."

At his press conference in London on Tuesday, Clegg said he wanted to end the "dismal cycle of repeat crime" by hardcore criminals. The majority of adults charged with riot-related offences already had a criminal record, he said. "We need to ensure that the treadmill, this dismal cycle of repeat crime, is stopped. We have thousands upon thousands of victims needlessly hurt because we have failed … to stop the cycle of repeat crime."

In an apparent dig at his coalition partners and the opposition, he said there was a tendency for parties to adopt "cardboard cutout" positions to social problems with one side blaming the problems on a breakdown in society and the other blaming government policy.

He rejected calls from the Tory backbenches for a marriage tax allowance to be introduced in the belief that it could help stabilise families. But he stressed the coalition was committed to giving tax relief to the poorest before the wealthiest after George Osborne's suggestion that the 50% rate of tax was under review.

"The coalition is very clear that what takes precedence if you've got money and the ability to provide tax relief to people is tax cuts for millions of people on middle and low incomes," he said.