A hardline "two strikes and you're out" automatic life sentence for serious sexual or violent offences will be brought into force shortly, the self-proclaimed "tough" justice secretary, Chris Grayling, has told the Conservative party conference.

The change, which will be brought in during December, will mean rapists and other criminals who commit a second serious violent or sexual offence will get a mandatory life sentence. Penal reformers have warned that the policy, which was imposed on Grayling's predecessor, Kenneth Clarke, by David Cameron, risks fuelling a fresh rise in the record prison population in England and Wales.

"Everyone deserves a second chance, but those who commit the most serious offences, crimes that would attract a sentence of 10 or more years, cannot be allowed to just go on and on causing harm, distress and injury," said Grayling. "Those people are a real threat to our society, and we must treat them as such."

His conference speech, with its "back to basics" headline announcements, marked a sharp break with Clarke's liberal criminal justice policies. Grayling, who explicitly promised to be a "tough justice secretary", confirmed he would strengthen the law on self-defence against burglars for householders, ensure there was a punitive element in all community sentences, and make much greater use of electronic tagging to enforce curfews and exclusion zones.

The home secretary, Theresa May, reinforced the theme with her announcement of a new "pick a punishment" power for victims of anti-social behaviour and her promise that Conservative candidates in the first elections for police and crime commissioners to be held on 15 November will have a "laser-like focus on cutting crime".

The police minister, Damian Green, left no Conservative in the hall in any doubt that there had been a change of management at the ministry of justice when he joked: "Theresa used to say she locked 'em up and Ken let them out. Now Theresa locks 'em up, and Chris throws away the key." Clarke's much trumpeted "rehabilitation revolution" barely got a mention during the hour and a half law and order presentation at the conference.

Around the fringe the new prisons minister, Jeremy Wright, made clear that the change went deeper than rhetoric. He explained his view that some short prison sentences worked for some offenders and that Clarke's approach of trying to stabilise the 86,000 jail population by capping it was no longer official policy. The intention of "putting some bite" into community penalties will no longer be as an alternative to short prison sentences.

"I've made no bones about my intention to be a tough justice secretary. That means I want our justice system to be firm, fair and transparent," Grayling said.

He said he would demonstrate that he was on the side of victims by changing the law on the use of force for people protecting their homes against intruders.

Householders who hit out "in the heat of the moment" needed to be treated as victims, not criminals: "That is why we are going to deal with this issue once and for all. I will shortly bring a change in to the law. It will mean that even if the householder faced with that terrifying situation uses force that in the cold light of day might seem over the top, unless that response is greatly disproportionate, the law will be on their side."

In interviews he said that would mean that if a burglar had already been laid out cold then the householder would not be justified in then stabbing him.

Juliet Lyon of the Prison Reform Trust warned of the impact on prison numbers of Grayling's new hardline approach: "The question remains whether the new justice secretary can secure prison as an effective place of last resort for serious and violent offenders or whether his tough line will propel numbers out of control at enormous social and economic cost."

Grayling also said he wanted to bring the same large-scale payment by results approach to work to cut reoffending as he had with the contracts to help the long-term unemployed through the Work Programme when he was employment minister. The justice secretary has put on hold both the reform of the probation service and the current payment by results pilot schemes while the details are worked out.

May's "pick a punishment" scheme will involve the victims of the 232,000 offenders each year who are currently given an out-of-court caution for low-level offences. To be known as the community remedy, police and crime commissioners are to be given a new duty to offer such victims a "menu of punishments" to chose from. These may include paying compensation, repairing criminal damage or a restorative justice option.

"They will be given a list of options," said May. "They might want something restorative or punitive. They might want it to be carried out nearby or as far away as possible. But what matters is that the punishment will be chosen by the victim."