Rehabilitation for some of the most serious sex offenders in jail has been branded "woefully inadequate" by opposition parties.
Figures show just a six percent difference in reoffending between sex offenders who do a treatment programme and those who do not.
Liberal Democrat justice spokesman Robert Brown obtained the figures through Parliamentary answers.
It comes after former prisons chief inspector Andrew McLellan warned in his final report that there are not enough rehabilitation places - and many of the most serious offenders will not sign up.
Mr Brown said on Sunday: "As a result, only a small proportion of long term sex offenders will have completed the treatment programme before release.
"It is extremely worrying that many serious sex offenders, who don't admit their crime, can simply opt out of treatment programmes.
"For those who do complete the programme these figures are further evidence, if it was needed, that sex offender rehabilitation in Scotland's prisons is woefully inadequate.
"Only six percent difference in re-offending between those who have completed a sex offender treatment programme and those who avoid it falls well short of what the public expects or a properly managed rehabilitation programme demands."
The figures also show that during 2007-08 a total of 93 offenders completed Sex Offender Treatment Programmes - about 69% of the number assessed as suitable for participation, although others could complete them later in their sentence.
"It is terrifying that convicted sex offenders can be released from prison having had little or no treatment," Mr Brown said.
"These are some of the most dangerous and predatory criminals in Scotland.
"Sex offenders are among the criminals whom the public are most afraid of yet the care given to their release back into society is not given proper and effective attention.
"The Scottish Government must speed up the development of an improved sex offender treatment programme. It must lower drop out rates while raising the number of offenders who participate and can re-enter society without public fear of them re-offending.
"The public demands no less."
