Serious offenders are escaping justice because of an erratic and inappropriate use of cautions and penalty notices, a think-tank has warned.
One in five sex offenders were given a caution last year, along with more than a quarter of those convicted or cautioned for violence against the person, Ministry of Justice (MoJ) figures showed.
Offenders are also escaping justice simply by not paying up after being issued with penalty notices, with up to £47 million having gone uncollected over the last eight years, the Policy Exchange report found.
Overall, a third of all offences brought to justice last year involved an out-of-court disposal (OOCD) such as a caution or penalty notice.
Some 406,000 out-of-court disposals were handed out in 2011, a third of all offences brought to justice. This was almost 70% more than the 240,000 issued in 2003, despite falling from the peak of 625,000 in 2007.
Karen Sosa, the report's author, said: "The evidence points to a continued problem of widespread inconsistency in their application and in the enforcement of out-of-court disposals. Current data also suggests that along with erratic use, there are a number of areas where OOCDs are being used inappropriately; to dispose of serious, indictable-only offences, and serial offenders are receiving multiple out-of-court disposals, with no formal system to monitor repeat use."
She went on: "Without greater transparency and focus, the widespread and erratic use of out-of-court disposals risks undermining public confidence in criminal justice agencies and weakening the power of the sanctions in the eyes of offenders."
It comes after Her Majesty's Inspectorate of Constabulary and Her Majesty's Crown Prosecution Service Inspectorate criticised the high use of out-of-court disposal such as a cautions, warnings or penalty notices for disorder last year.
A Ministry of Justice spokeswoman said: "Out-of-court disposals allow the police to deal quickly and proportionately with low-level, often first-time offending which does not merit prosecution at court, freeing them up to spend more time on frontline duties. But we know there have been problems, and we are determined to address them. We have swept away all targets in this area, in line with our intention to give back discretion to professionals such as police officers and we are working on clearer guidance to help ensure that out-of-court disposals are used appropriately and effectively."
She went on: "We are introducing a 24-hour national fixed penalty database which will greatly assist police officers in deciding on the suitability for such out-of-court disposals and will help reduce reoffending and non-payment. We will be setting out further plans to improve how they are used in the forthcoming Criminal Justice White Paper."