There was a 40 per cent rise in the number of addicts waiting more than a year to be assessed for treatment.
The figure soared from 353 to 495 between April and June compared to the previous three months, a report obtained by the SNP shows.
Their drugs spokesman, Stewart Stevenson, said it showed services could not cope with demand.
He said: "Waiting times like these are simply shameful.
"They are particularly unacceptable when we have a strategy that rightly encourages addicts to seek help and take personal responsibility for their lives."
The figures were provided by the NHS after questions from the Banff and Buchan MSP.
They also showed around 800 people were waiting over six months for an assessment after being referred by a doctor.
Addicts who had been assessed also faced longer delays to start their treatment.
In June, 331 addicts had waited more than a year just for counselling - 30 more than at the start of the year.
And there were 376 people waiting over a year for rehab either in the community or on a residential detox programme - up slightly from the start of the year.
A further 190 were waiting a year for drug treatment - twice the level of January. Stevenson added: "The fact that 495 patients have had to wait over a year, and are still waiting, is unacceptable.
"Nicola Sturgeon raised this important issue at First Minister's Questions eight months ago.
But these figures show little progress has been made by this Labour and Lib Dem government since then."
Scots Tory leader Annabel Goldie also criticised efforts to cut drug use, claiming the failure added to crime.
A Scottish Executive spokeswoman claimed the figures were unreliable.
But she added: "We know some people have unacceptably long waits for treatment.
"Three-quarters of an additional £4million allocated last year was awarded for proposals to reduce waiting times."
[for the original story click on Daily Record]