The failure to rehabilitate tens of thousands of criminals serving short prison sentences in England and Wales costs the taxpayer up to £10 billion each year, according to a new report.
The National Audit Office (NAO) found that many prisoners on short-term sentences spent all day in their cells, rather than being engaged in training or rehabilitation programmes.
The NAO said that activities for prisoners are "inadequate", and little is known about which schemes work.
Prisoners serving less than a year have the highest reoffending rates among other prisoners, with an average of 16 convictions each.
Many of those serving short sentences are hailed for theft or minor violent crimes, and are often homeless or dependent on drugs or alcohol. While they can serve as little as 45 days, there is little "appropriate assistance" to prevent them from falling back into a cycle of crime.
Approximately 60,000 prisoners are jailed for less than 12 months each year, costing the country £300 million annually.
The report concludes that short jail terms are costly for the taxpayer. A six-week jail term costs £4,500. This is £300 more than a highly-intensive two-year community order involving unpaid work and rehabilitation schemes.
The government said it would take the report's recommendations forward.
