Boris Johnson ordered an urgent review of sentencing policy as he vowed to ‘come down hard’ on crime.
The Prime Minister said dangerous criminals must be taken off the streets and punishments “truly fit the crime” if the public was to have confidence in the justice system.
He also announced an extra £85 million for the Crown Prosecution Service (CPS) to help it manage its caseload over the next two years.
The move follows a series of announcements over the weekend in which Mr Johnson promised to “come down hard” on crime.
They included a £2.5 billion programme to create 10,000 additional prison places and the extension of enhanced stop-and-search powers to police forces across England and Wales.
It will fuel speculation that Mr Johnson is preparing the ground for an early general election amid continuing deadlock in Parliament over Brexit.
The sentencing review has been instructed to start work immediately and to report back to No 10 in the autumn, just as the country may be going to the polls.
Its remit is to look at the rules governing how and when violent and sexual offenders are released from prison.
Currently, offenders sentenced to 12 months or more serve the first half of their time in prison and the second “on licence” in the community, where they may be subject to recall.
The review will consider whether changes to legislation are needed so that more time is spent in jail.
Mr Johnson will highlight the approach at a Downing Street round table bringing together leaders from the police, probation and prison sectors on Monday.
He said: “Dangerous criminals must be kept off our streets, serving the sentences they deserve – victims want to see it, the public want to see it and I want to see it.
“To ensure confidence in the system, the punishment must truly fit the crime. We have all seen examples of rapists and murderers let out too soon or people offending again as soon as they’re released.
“This ends now. We want them caught, locked up, punished and properly rehabilitated.”
However critics warned that there was no evidence that longer sentences would result in a reduction in crime.
Liberal Democrat justice spokeswoman Wera Hobhouse said the UK already had the largest prison population of any country in Western Europe and that a different approach was needed.
“For years, Labour and Tory ministers have made sentences longer and longer, without any evidence that they prevent crime,” she said.
“It may sound tough, but it hasn’t made our communities any safer. All it does is overcrowd our prisons and waste millions of pounds.
“We do need a sentencing review, but its aim should be to reverse decades of pointless sentence inflation. Instead of just talking tough, it’s time ministers look at the evidence.”
The Solicitor General, Michael Ellis QC, said the additional £85 million for the CPS would ensure it was equipped to deal with an increase in cases brought to them by the police.
Chris Henley QC, chairman of the Criminal Bar Association, added: “The criminal justice system is severely underfunded, as a result of relentless cuts over the last 10 years.
“Any change to that direction of travel is to be welcomed. The CPS is desperately in need of significant investment to improve its capacity to deliver effectively for the public, but this has to be seen as a modest first step in the rebuilding process.
“Far more will be needed across the system including more substantial sums to the entire prosecution system and the Ministry of Justice including the courts service to restore public faith in our criminal justice system where increasingly those who commit crime walk free and the innocent risk being convicted.”