The top prosecutor has demanded an end to the use of police cautions to deal with thousands of serious assaults every year amid concern that the justice system is failing to rein in violent offenders.

Keir Starmer, QC, the Director of Public Prosecutions, is seeking a review of so-called “instant justice”, with up to 40,000 assults each year now dealt with by on-the-spot cautions.

These include a 15-year-old boy who was cautioned for rape and a man who was cautioned for smashing a beer glass into a landlady’s face at a pub, The Times can reveal.

Cautions were introduced to deal with minor offences — such as shoplifting — with the aim of reducing legal expenses and leaving courts free to deal with the most serious crimes.

But one senior circuit judge warned that it was only a matter of time before a domestic assault was dealt with by a caution and the victim was subsequently murdered.

Responding to growing concern about the widespread use of cautions, Mr Starmer told The Times that no offence above the level of common assault should be dealt with “out of court”.

There was now a case, he added, for a new scheme covering all “out of court” penalties that would specify what offences can be dealt with at what level.

Mr Starmer said that there was a “proper place” for trivial offences to be dealt with outside the courts through fixed penalty notices, cautions and conditional cautions.

But the system had developed in a piecemeal and “incoherent way” and there now needed to be a single coherent scheme.

“There is now a case to be made for a review,” he said. “My view is that there should be a structured tiered approach which specifies what case will be dealt with at what level — and will be transparent.”

Mr Starmer said he had already issued guidelines to his prosecutors, stating that “violent offences — that is, all those above common assault — should go before the courts”.

He added: “I have also personally asked for monthly returns from each prosecuting area in England and Wales on cautions handed out, so I can see what they are being given for.”

The aim was to put the figures on the Crown Prosecution Service website “so the public can see” and to create greater accountability.

Prosecutors have had powers since 2005 to hand out conditional cautions, which are like a suspended sentence and can include some hours of community service.

Since then they have issued nearly 20,000. In the past year the rate was between 600 and 700 a month or about 8,000 a year.

The police hand out cautions and fixed penalty notices, usually £80 fines, which ministers are keen to extend to an even wider list of offences than at present.

In one case of “instant justice” a boy aged 15 was cautioned for rape. His solicitor, Richard Haigh, said: “I was dealing with this boy on another matter — he is now 17 — and this caution was on his record.”

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