Courts are making greater use of community sentencing, with the number given increasing by 57 per cent.
The report states: "Prison overcrowding is a well-known fact. What is less well known is that community sentence caseloads are also overcrowded. The effect is far less graphic than images of overcrowded jails but the impact is equally damaging."
But often, the reports notes, these sentences are given to those who would usually receive a fine, rather than a custodial sentence, meaning that the prison populations are not being appeased by the increase in community sentencing.
Richard Garside, director of the CCJS, said: "This analysis suggests that community sentences are being used as a complement to prison, rather than an alternative to it.
"This report offers an invaluable starting point for anyone interested in understanding and discussing the potential role and the potential limitations of community sentences."
When asked about the report, a spokesman for the Department of Constitutional Affairs said the government could not comment on sentencing issues until the newly formed Ministry of Justice came into effect.
Today marks the official launch of the new government department, which will handle matters of criminal justice previously under the umbrella of the Home Office.
The Kings College report also raises concerns over the lack of information about the kind of people who are given community sentencing.
It shows that nearly two-thirds of those on sentences are below the literacy and numeracy level expected of an 11-year-old. In addition, more than half of those on a community sentence are unemployed.
About a quarter have a drug problem and almost half are considered to have an alcohol problem, something which Enver Solomon, deputy director of the CCJS, believes should be looked at.
"Given the expansion in community sentence caseloads it is surprising how little information and analysis there is about these sentences and the people who serve them, especially compared to the attention given to prisons," Mr Solomon said.
"Yet there are important questions to be asked about the capacity within probation to cope with the increase. At the same time there is a real need for greater scrutiny to consider whether or not community sentences can effectively address the needs of offenders who experience severe social exclusion."
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