A higher proportion of young offenders (58%) returned to custody within two years, compared to 46% of adult prisoners.

Behind bars

The figures for those released in 2002 also revealed that men were more likely to end up back in jail after serving a sentence, with 49% returning within two years, compared to 39% of women.

Most of those who returned did so within just six months of their release.

A total of 52% of those who returned to prison did so within this time, while 76% were back in custody within a year of their release.

Those most likely to return to prison were those who had committed crimes of dishonesty - 68% of the men jailed for this were back in prison within two years, as were 48% of the women.

Scottish Conservative leader Annabel Goldie said the figures illustrated the need for a comprehensive rehabilitation programme to reduce re-offending.

Ms Goldie said: "No doubt some people will use the statistics as 'proof' that prison does not work, but this is simply not true.

"International studies have shown that prison works as a punishment and as a deterrent.

"I'm concerned the Scottish Executive's half-baked measures on early release will not solve the problem, because prisoners are still potentially going to be let out halfway through their sentence."