Managers policing supposedly tough community service orders allowed criminals to escape punishment for unacceptable excuses on a regular basis, an independent watchdog found on Thursday.

Instead of being more rigorous in checks on offenders, managers instead allowed too many "unacceptable" excuses such as forgetfulness, or not producing a doctor's note to prove illness, the National Audit Office report found.

Inspecting five areas across England and Wales, the watchdog found that in almost one in 10 cases criminals escaped punishment for forgetfulness, over sleeping, or for failing to provide acceptable sick certificate.

"In the cases we reviewed we found... variations in the number and type of absences accepted by offender managers, and that occasionally offender managers may accept "unacceptable" reasons when more rigorous enforcement would be more appropriate," the report said.

It also criticised failures by the National Probation Service, which it said did not know how much an order cost taxpayers or how many it could enforce.

The chairman of the public accounts committee, Edward Leigh, said in a statement that too many offenders were escaping punishment or rehabilitation.

"Some offenders are not completing community order sentences imposed on them by the courts because of failures in the National Probation Service," he said. "The law-abiding taxpayers of this country deserve better."

Shadow Justice Secretary Nick Herbert attacked the government for being more concerned with public relations.

"Instead of launching a PR campaign to persuade courts to use community punishments as part of a desperate drive to reduce the prison population, the government should address the fact that too many community sentences are weak and unenforced," he said in a statement.

Justice minister, David Hanson, defended the system but confirmed a review was being carried out in light of the NOA report. "Tough community sentences that effectively address offenders' behaviour can get right to the heart of the offending," he said in a statement.

"The sentences provide punishment and restrict liberty for individuals in order to change patterns of behaviour in often chaotic lifestyles."