Half of all criminals aren't even hauled before a court

Instead, they escaped with on-the-spot fines, cautions and warnings, said the chief inspector of the Crown Prosecution Service.

Stephen Wooler said that the "over-zealous" use of such penalties - rather than taking criminals to court - could damage public confidence.

And, in his annual report, he warned yesterday that the public could begin to view the criminal justice system as a "revenue-raising initiative".

As recently as 2003, 68 per cent of offences brought to justice involved convictions in the courts. But Mr Wooler said that, last year, the figure was between 40 and 50 per cent.

The court conviction figures reflect the dramatic changes made to the justice system by Labour, forced through despite protests from crime victims and opposition MPs. Cannabis possession is now punished by a simple ticking-off, since the controversial decision to downgrade the drug to Class C in 2004.

And on-the-spot fines have been introduced for shoplifting, criminal damage, being drunk and disorderly and other yobbish crimes. Only half are ever paid.

There has also been a sharp rise in cautions, with 8,000 rapists and other sex offenders being let off with a mere reprimand over the past five years.

In 2005, the latest year for which total figures are available, some 51,000 violent attackers were simply handed a caution, which carries no criminal or financial penalty - an increase of more than a third on 2004.

This includes 757 who inflicted potentially fatal wounds and 588 who threatened to murder their victim.

In total, 299,000 cautions were handed out - up 17 per cent on 2004.

This includes 199,000 children given reprimands or final warnings. There were also 146,500 drunks, thieves and thugs who escaped with onthe-spot fines and 57,700 cannabis smokers given a ticking-off.

Some 22 rapists were cautioned. Most were either elderly or very young, or committed the offence many years ago. A total of 390 were let off with a caution for having under-age sex and three for child porn offences.

Under the Government's rules for counting the number of offenders brought to justice - a key police target - fines and cautions carry the same weight as a conviction through the courts.

Critics, including rank-and-file police, say this has placed enormous pressure on officers to take the easier option.

Mr Wooler's report said that a snapshot survey, taken in February this year, found 49 per cent of offences brought to justice - all the crimes which police counted as solved - were convictions in court.

A further 8.9 per cent were offences "taken into consideration", where an offender being prosecuted admits to other crimes.

A staggering 26 per cent were cautions, 9.6 per cent were fixed-penalty notices, onthespot fines, and 6.5 per cent were formal warnings for cannabis possession.

Mr Wooler said: "Typically, prosecutions now account for between 40 and 50 per cent of the offences brought to justice within a criminal justice area.

"The power to fine is now vested in many authorities and brings the risk that overzealous use may lead groups of citizens to believe that they are in reality the subject of a revenue-raising initiative."

He added that, if officials are "incentivised" to hand out as many fines as possible, this could cause "substantial damage to public confidence".

Only 42 per cent of the public currently believe criminal justice agencies are effective in punishing criminals, according to research cited by Mr Wooler.

Yesterday it also emerged that in one city, Exeter, the number of cautions alone is the same as the number of court prosecutions.

In 2006 927 offenders were cautioned, warned or reprimanded while 932 were prosecuted, according to figures released under the Freedom of Information Act.

Crimes for which cautions were handed out included sexual offences, assault, fraud, forgery, drugs offences and criminal damage.

Shadow Home Secretary David Davis said: "It is disgraceful that so many crimes are going effectively unpunished.

"This a consequence of Labour's policy of keeping criminals out of the justice system at all costs - but passing cautions so that they can claim a crime has been dealt with.

"This is all to fiddle the figures, while doing nothing to tackle the scourge of rising crime on our streets."