FOUR in 10 serious offenders are being let off with a caution, The Daily Telegraph can disclose.

In some police force areas more than half of offenders who could expect to face a crown court are instead given a "slap on the wrist''.

The number of cautions being given to violent criminals has risen by 82 per cent in five years. Cautions given to burglars have increased by a quarter over the same period while cautions for robbers and sex offenders have gone up by almost half.

The figures come as official crime statistics published today are expected to show rises in robbery and burglary amid fears that the economic downturn is leading to more offences.

David Ruffley, the shadow police minister, who unearthed the most recent rises, said: "Police cautions are being used instead of prosecutions. More serious offenders are facing 'cautions not court'.''

When Labour came to power it pledged to be "tough on crime, tough on the causes of crime'' but, last month, figures showed that almost four out of 10 crimes are not being investigated by the police.

Even when crimes are dealt with, many offenders are escaping with soft punishments. Cautions are supposed to be handed out for lesser offences but have increasingly been given for more serious crimes. They can only be used if the offender admits guilt, but he then avoids the shame of a court appearance and the likelihood of a harsher sentence.

It is left to the discretion of the police as to whether the caution is recorded on the Police National Computer. This approach means that some offenders who have been cautioned do not receive a criminal record.

Simon Reed, the vice-chairman of the Police Federation, which represents 140,000 rank and file officers, said there was "still a question mark'' over the use of cautions for some offenders.

"They have a place for first-time offenders, young people and minor offences,'' he said. "But on the face of it, people are getting away with very serious offences with just a caution.''

In 2007, the most recent figures available, 40 per cent of criminals guilty of the most serious offences were given a caution - 205,100, compared with 313,300 who were dealt with in the courts. It was the second year running that the proportion had reached that level.

The figures relate to those guilty of either an indictable offence - a crime that would normally be dealt with in a crown court - or a so-called either-way offence, which can be dealt with by magistrates or crown courts.

In eight police force areas, half or more of those guilty of serious crimes are dealt with via cautions. They are Bedfordshire (50 per cent), Essex (56), Hertfordshire (53), Northamptonshire (55), Nottinghamshire (53), Staffordshire (52), Warwickshire (54) and Dyfed-Powys (57).

The increasing use of the cautions drives at the heart of Labour's pledge to tackle law and order.

Violent offences have almost doubled since the party came to power and its failure to manage prison overcrowding has led to accusations that courts and the police are under pressure not to jail people.

Lyn Costello, of the campaign group Mothers Against Murder and Aggression, said: "It is a total insult to victims. Crime is not going to go down if we keep cautioning people.

"What is the point in having tough sentences if we are not going to use them? If we are going to talk tough then let's start acting tough.''

The number of cautions for violence against the person went up by 82 per cent between 2003 and 2007, from 28,760 to 52,335. Some 56 per cent of violent offenders now escape a court appearance in this way.

A Ministry of Justice spokesman said: "The Government is committed to ensuring the most serious crimes are investigated and prosecuted.

"These statistics show a greater number of serious crimes are being brought to justice, and a greater proportion of serious offences are going before the courts rather than being dealt with by cautions.''