Mr Treble, its deputy forensic business manager, said: "With ever increasing amounts of drugs coming into the country and use going up, responsibility for controlling drug abuse has to an extent transferred to the employer because he has a duty of care to those on his premises.
"However, drug-testing is not something to be done lightly. It is not just a question of saying, `Right you lot, from next week you have to produce a sample when we say so.' Testing should only be part of a broader drugs policy which covers what you do if someone does test positive."
The laboratory, based in Teddington, Middlesex, carries out about 65,000 tests a year on urine samples for the armed forces and 90,000 a year for the prison service, where initially 40 per cent of inmates tested positive.
The laboratory was privatised last year and hopes to tap into the growing private sector market. So far, it has about a dozen private clients, requiring about 30,000 tests a year.
Prices are typically pounds 40 each for a small number of tests though the cost is generally reduced substantially on big contracts.
Mr Treble says it is important that employees are able to question the testing laboratory's qualifications, given that it is relative easy to get wrong results, and the "chain of custody" provided for the sample. If a sample tests positive, the individual should have the right to challenge the finding. The laboratory keeps positive samples for a year and the written records for six years.
There is a whole underground literature in America on beating tests by contaminating, diluting or substituting samples. "They are basically useless, but there are no limits to people's ingenuity - we have found substances which certainly did not come out of any human body," he says.
Another service is Medscreen, set up 10 years ago. It has about 500 private clients, requiring anything between 20 and 20,000 tests a year.
"People now realise that drugs and alcohol problems have to be addressed - one person can endanger lives and even the future of the company, so a sound drugs policy can benefit everyone," says Lindsay Hadfield, Medscreen's policy and education consultantnReuse content