Violent and sexual criminals could be serving more of their sentences behind bars after an urgent review of sentencing ordered by the Prime Minister.
Boris Johnson 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.
It came as part of a series of announcements to crack down on crime in which the PM said he wants rapists and murderers “caught, locked up, punished and properly rehabilitated".
Mr Johnson also pledged an extra £2.5 billion to create 10,000 more prison places, as well as £85 million to help the Crown Prosecution Service (CPS) manage its caseload over the next two years.
In addition, the review will look at the extension of enhanced stop-and-search powers to police forces across England and Wales.
Mr Johnson 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."
However, critics have warned that there is no evidence that longer sentences would result in a reduction in crime.
"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,” said Liberal Democrat justice spokeswoman Wera Hobhouse.
Charlotte Pickles from the Reform think tank echoed Ms Hobhouse, labelling the criminal justice reforms "a monumental waste of money".
She added: "Intelligent investment is clearly need, but these pledges are costly election baubles, not a serious attempt to make this country safer."
Meanwhile, Katrina French, chief executive of Stopwatch charity, said: “We are an a-political organisation, we work across Parliament but the legacy of Theresa May is being damaged in terms of what she did via the best use of stop and search schemes... this isn't about policing, it’s about undoing her legacy and that’s very damaging."
The sentencing review has been instructed to start immediately and report back to No 10 in the autumn, fuelling speculation that Mr Johnson is preparing for an early general election amid the ongoing Parliament deadlock over Brexit.