Labour says government cuts are "undermining" the justice system
About 50% of criminals convicted of sex offences, violence and burglaries in England and Wales in 2012 were not sent to prison, it has emerged.
Of paedophiles who abused children under the age of 13, 107 - nearly half - were not jailed.
The figures were released following a parliamentary question from shadow justice secretary Sadiq Khan, who said the news was an insult to victims.
The government said it was working to give courts tough sentencing powers.
The Ministry of Justice figures also showed 40% of convicted robbers - about 5,000 people - and 51% of drug dealers were not jailed in 2012.
In cases of sexual assault, 49% - more than 2,300 offenders - were not given custodial sentences.
Among those convicted of rape, 94% were sent to prison, the vast majority for more than four years.
Mr Khan said government cuts were undermining the justice system.
"Some of these crimes are so serious and violent that members of the public rightly expect them to lead to a prison sentence," he told the Daily Telegraph.
"Justice done on the cheap like this risks prisoners reoffending rather than being reformed, which means more victims and misery.
"This will be an insult to many victims of crime who want to see those who committed crimes against them properly punished and rehabilitated."
Justice Secretary Chris Grayling said the government was working to ensure the "toughest sentencing measures" were available to the courts.
He told the Telegraph he would "take no lessons" from Labour, who he said "let thousands of offenders off with a slap on the wrist" and failed to tackle the reoffending rate.
"Our reforms will help criminals [move] away from crime - and help them stay away from it," he said.
Mr Grayling replaced Kenneth Clarke as justice secretary in the autumn of 2012 - the year these figures relate to - and BBC political correspondent Chris Mason said that move by David Cameron was widely seen as a signal that he wanted to appear tougher on law and order.