In the three years since penalty notices for disorder (PNDs) were introduced as the latest weapon in the war on petty crime, this much has become clear: police forces have taken to them with alacrity. More than 360,000 PNDs, or one every three minutes, have been issued for offences ranging from shoplifting to antisocial behaviour that would have led to verbal warnings, written cautions or prosecution via the magistrates’ courts before 2004. This substantial shift towards street-level punishment has eased the pressure on still-overburdened courts and prisons. It has also helped the Government to hit targets for tackling crime. Whether it constitutes justice or makes people feel safer is another matter.

The evidence so far suggests that PNDs have little deterrent effect and in some cases have triggered a rise in crime. The conclusion for those considering whether to expand their use must therefore be: this far, and no farther.

There is nothing wrong with setting or meeting crime-reduction targets. Nor is there much doubt that in thousands of cases PNDs have provided better outcomes to crimes of vandalism and disorderliness than would have been achieved with warnings or failed prosecutions. But the PND experiment is gravely undermined if it fails to build public confidence in the criminal justice system as a whole, or even erodes it. There is a real risk of this happening.

Not only do PNDs bypass due process by entrusting the traditionally separate functions of judge, jury and police to a single person; they are also being actively promoted to police forces as a way of meeting goals for what the Home Office calls “offences brought to justice”. The danger here, as the Crown Prosecution Service has noted, is a perception not just of box-ticking at any price, but of justice subordinated to revenue-raising. Finally, the soaring use of PNDs – up by nearly 40 per cent from 2005 to 2006 – masks an equally striking fall in court convictions, from nearly 70 per cent to 53 per cent of all cases brought to justice since 2004. Some of this reflects a fall in certain categories of crime, but the overall conviction rate, at three per hundred crimes committed, remains abysmal.

The Labour manifesto of 1997 pledged to bridge what it called this “justice gap” between crime and conviction. The Government has made progress. There were just two convictions per hundred crimes ten years ago. But it cannot be satisfactory that more than half the crimes that officials claim have been brought to justice have never, in fact, been judged by a court. On-the-spot fines were handed out for nearly 10 per cent of these crimes last year. Half of them, according to the CPS, are never paid, handing a major new debt-collection task to magistrates’ courts that were supposed to have been freed up by PNDs and other fixed penalties to handle more serious crime. And those issued for shoplifting may actually have boosted it: three months ago the British Retail Consortium complained that shoplifting was on the rise because petty thieves knew they were not risking prison.

Britain’s prisons are full. Its courts struggle with a perpetual backlog. In these circumstances, on-the-spot fines make sense for Friday-night layabouts, but not as the basis of a new approach to crime. The Government should think hard before extending their use.