Keir Starmer has accused Boris Johnson of having “no respect for law and order” as he claimed public confidence in the justice system had collapsed under the Tories.
New figures released by Labour show a quarter of reported crimes are now going unpunished.
Sir Keir said there was a “victims’ crisis” and a “collapse of confidence” among those seeking to report offences, with over 40 per cent of violent crimes and rapes going unpunished due to victims being unwilling to press charges.
The former director of public prosecutions launched the attack ahead of the local elections in less than three weeks’ time.
Labour has made crime a key element of its campaign in the run-up to the 5 May vote, at a time when the government is under pressure over a series of parties during Covid lockdowns that saw Mr Johnson fined last week.
Sir Keir said: “Faith in the criminal justice system to deliver for victims is a pillar of a civilised country. Under the Conservatives, it’s being devastatingly undermined. As ever with this prime minister, the institutions he vows to protect are being damaged.
“As director of public prosecutions, I saw the essential value of victims’ knowing that they would be backed to the hilt until justice was served. Twelve years of Conservative government have decimated the system, leaving too many people in an emotional and financial limbo, and more likely to give up on getting the justice they deserve.
“This is all in addition to a prime minister who shows no respect for law and order. How can the country have faith in the system if even when justice is served, it apparently has no consequences?
“Britain deserves better. With Labour, victims will come first, and criminals will be punished.”
Home Office data shows 25.5 per cent of cases in the year ending September 2021 were closed due to victims not supporting further action, according to Labour.
Of these, 20.9 per cent had a suspect already identified, it said.
The latter figure was up from 20.7 per cent in the year to September 2020, and 18.2 per cent in the year to September 2019.
It is more than treble the first figure recorded in the relevant Home Office dataset, which was 6.9 per cent in the year to March 2015.
Mr Johnson is said to be preparing to make a statement in the Commons once MPs return to Westminster following the Easter recess.
Despite being fined by the Metropolitan Police for his birthday party held in the Cabinet room in June 2020, while coronavirus restrictions were in place, the prime minister is expected to tell MPs on Tuesday that this should not be the focus of politicians.
