Clive Fairweather, who released his annual report on Thursday, said new accommodation meant "it is now possible to predict an end to overcrowding" in prisons.

The BBC's Reevel Alderson reports on Clive Fairweather's latest prison inspections.

But he added: "Drugs have now taken over from overcrowding as the central problem for Scottish prisons, though efforts to tackle drug abuse are being intensified through education and rehabilitation programmes."

The reduction in overcrowding is being attributed to new facilities, including the opening of the country's first private prison at Kilmarnock and the prison population stabilising at about 6,000.

Although highlighting drugs as a serious problem the inspector said there were signs it could be tackled, because there are indications more prisoners are coming forward to say they want help to kick their habit.

He cited Dungavel prison, where he said "good management, tough enforcement and the incentive of open conditions" reduced random mandatory drug testing figures from 60% almost 10%.

HMP Kilmarnock has helped ease overcrowding

Random drug testing has been in place for two years and the average number of prisoners who tested positive in 1998-99 was 25%, as opposed to 29% in 1997-98.

The inspector attributed drink and drug addictions as contributing factors to Scotland's "disproportionate rise in prison suicides".

The rate has doubled since 1992 and is much higher than in England. In 1998-99 there were 14 suicides in custody and 13 the year before.

He said he was not sure if there would be any short-term solution to the problem, despite the prison service overhauling its suicide policy.

In the past, overcrowding had overshadowed everything the prison service had tried to achieve, said Mr Fairweather.

But with that problem easing, improvements were being made in efforts to stop prisoners re-offending.

"I wish to highlight what is now being achieved for all women prisoners at Cornton Vale and the excellent standards being maintained at Inverness," he said.

Clive Fairweather: Drugs a big problem

"Nevertheless, I should also draw attention to the mediocre conditions at Longriggend and Low Moss, the latter, with its high turnover of drug abusers, having now become Scotland's most violent prison."

The chief inspector raised concerns that not enough is being done to keep young people out of jail.

He said unless something was done to help them their chances of re-offending were significantly higher.

But overall he remained upbeat and added: "As the century ends there are encouraging signs that some of the 19th century conditions which previously existed in Scotland's prisons are now beginning to disappear."

The report was welcomed by Susan Matheson of prisoners' support group Sacro.

But she warned there is no room for complacency and pointed out that Scotland is still sending more people to prison than any other European country except Portugal.