The Metropolitan Police are routinely issuing cautions to muggers, it was revealed today.

The force handed out 329 cautions for street robbery last year - even though the offence carries up to five years in prison.

New figures also show that in London last year, police issued a total of more than 14,000 cautions for serious crimes including assault, robbery, burglary, car crime and hard drug offences.

In nearly every case there would have been sufficient grounds for a conviction because the suspect was caught and admitted guilt.

The Home Office describes a caution as 'a warning given to adults who admit they are guilty of first-time minor offences, such as vandalism or petty theft'.

But information obtained under the Freedom of Information Act show police frequently resort to using cautions when dealing with much more serious crimes.

The figures reveal that in the financial year 2005-6 a series of offences which would normally be prosecuted ended in a caution, including:

• 474 for burglary.
• 617 for car theft.
• 1,477 for drug possession excluding cannabis - one in four being caught with class A or B drugs.
• 5,216 for shoplifting - with a total of 41,036 shop thefts recorded last year, this means that one in eight of those caught receive only a warning.
• 5,955 for assault, excluding common assault, out of a total of 84,372 attacks - equating to a caution for one in every 14 people apprehended for violent assault.

Blair Gibbs, spokesman for the TaxPayers' Alliance, which obtained the figures, said: "No wonder violent crime is out of control when criminals know there's often no punishment at all.

"We can't hope to have safer streets when the police are refusing to charge criminals for serious offences, even when they manage to catch them. Taxpayers and victims of crime deserve better."

The figures will come as a further embarrassment to the justice system after it emerged that nationally only one crime in every 100 leads to a conviction in the courts.

Home Office figures showed that although crime rose last year the number of offenders taken to court dropped by eight per cent.

Opposition MPs have blamed an increasing use of fines and warnings as well as cautions.

A police spokeswoman said: "Every case is considered on an individual basis and the overriding factors are whether a caution is appropriate to the offence and the offender and whether a caution is likely to be effective in the circumstances.

"The aims of the caution are to deal quickly and simply with less serious offences, to divert offenders where appropriate from appearing in the criminal courts and to reduce the likelihood of re-offending."