However, the Tele has learned the charges dropped involved cases in the city where small or trace quantities were found and the backlog may be as long as nine months. It is understood some officers are angry their work is being undone.

A force spokeswoman said the backlog affected only “a very small number of minor cases”.

When asked about the exact numbers abandoned and why other force areas which use the laboratory were not involved, Detective Superintendent Jim Cameron referred inquiries to Dundee’s procurator fiscal.

But the fiscal’s office quashed any notion there was an arrangement in place with Tayside Police.

In a joint statement on behalf of the force and the PF’s office, a Crown Office spokeswoman said, “There is absolutely no question of an agreement between Tayside Police and the Dundee fiscal to drop cases simply to clear a backlog.

“Drugs have a corrosive effect on our communities, and both the police and the fiscal service are committed to treating all such offences seriously.

“Cases reported to the fiscal are considered on an individual basis, and a decision on whether to proceed is based on the specific evidence and circumstances of that case in accordance with the Lord Advocate’s guidelines.”

However, pressed further, the spokeswoman said that undue delay was a potential reason for dropping a case, although she was not in a position to say how many cases had been dropped in Dundee and Tayside for that reason.

She was also unable to deny that drugs charges may have had to be dropped because of hold-ups in analysis, adding, “We would have to look at every single drugs charge and the reason it did not proceed to produce that information.”

Det. Supt. Cameron said the average turnaround time for analysis is three months, but that the fiscal decides whether substances should be scanned at all, particularly where only trace amounts are discovered.

He said the backlog reflected the force’s commitment to drug crime, citing an increase in the detection of simple possession.

“This is not down to a funding shortage,” he said. “It is due to the high turnover of staff, recruiting and training new staff members and making sure that new staff members are suitably qualified to analyse drugs samples.

“It also reflects the high level of activity that Tayside Police carries out in drugs enforcement.

“For example, the number of cases involving simple possession of drugs increased from 2295 to 2608 in the last year. This is a continuing trend which illustrates our commitment to this area of work.

“While we are not aware of any concerns, Tayside police officers will continue to report anyone found in possession of drugs to the procurator fiscal.”