Brigadier Hugh Munro told MSPs he was concerned that dozens of sex criminals are being freed directly from their jail cells without being "tested" first in open prison.

Citing conditions in Dumfries Prison, he said many are stuck in a "penal cul-de-sac" because they undergo no rehabilitation before being let out.

His intervention at Holyrood's justice committee came as official figures disclosed there are 3,222 sex offenders in the community, the highest total on record since at least 2007.

The number convicted of a violent or sexual offence after being released nearly doubled from 39 last year to 69 in 2011/12.

Brig Munro told the committee he was "surprised" to find only two sex offenders in Castle Huntly when he inspected the open prison near Dundee earlier this year.

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"Yet we were releasing, in the previous 12 months, about 150 directly from closed conditions not having been tested under open conditions," he said.

"I don't know whether this is right or wrong, what I am saying is we need some evidence and some help in this matter in terms of risk."

He told MSPs some steps have been taken to rehabilitate offenders, including giving them their own unit at Glenochil prison near Stirling, but concerns remain about how they are handled.

"What I really worry about is that at some stage offenders are going to be released from those conditions directly back to the community," he concluded.

A major report on Scottish policing, published yesterday, showed that 3,946 sex offenders are being monitored in the community by the authorities.

This was a slight increase on the previous year and 210 more than two years previously. The Tories reiterated their call for sex offenders to be subjected to satellite tracking.

John Lamont, the party's chief whip, said: "We also think if the Scottish Government dropped its automatic early release, as it has promised to do on more than one occasion, this would allow such offenders to serve fuller sentences and have more chance of being rehabilitated."

Kenny MacAskill, the Scottish Justice Minister, recently announced that criminals are to be tracked by satellite, a move that if successful could be extended to sex offenders.

However, he caused consternation by handing the £13 million contract to G4S, the firm at the centre of the London Olympics security debacle.

A Scottish Prison Service spokesman said the organisation is considering how to move more sex offenders to open prisons "while ensuring public safety is maintained".

A Scottish Government spokesman said: "The monitoring of sex offenders in Scotland is tougher than ever before and many are required to register for long periods of time, with some registering for life."