Workplace drug tests are going to become more common, according to some experts, with figures showing around one in eight people has already been asked to take a test.

But some unions say the tests target certain groups of workers and jobs only, despite drug use pervading every level of the workforce.

A poll of 5850 Australian drug and alcohol users conducted for The Global Drug Survey in partnership with Fairfax Media, found workplaces could be right to worry.

Over a third of full-time workers said they have taken drugs (including alcohol) within two hours of starting work. Some respondents said they now use newly invented and proven dangerous psychoactive drugs, just to avoid the dragnet of the testers.

The deputy director of research at the National Centre for Education and Training on Addiction says drug use is contributing to waves of “presenteeism”; the act of turning up to work either intoxicated or hung-over.

“Obviously the biggest threat from workplace drug use is safety,” director Ken Pidd has told the Sydney Morning Herald.

“If people are intoxicated at work, but there is a much larger picture around absenteeism, or even presenteeism, related to use outside the workplace,” he said.

Pidd says in a recent review of points in favour of drug testing that there was little proof they improved safety, apart from a few circumstances such as mandatory alcohol testing of truck drivers in the US.

“It is a particular issue for urine testing, which doesn't actually detect impairment, just prior use,” he said.

He said that for the most part, drug use rates in the workplace are quite low in Australia, though they do spike in fields including hospitality and finance.

“Workplace drug use tends to be in line with drug use in the broader population,'” he said.

“There are some types of drugs that are increasing, such as prescription drugs, so they are likely to be increasing in the workplace as well.”

He says there is a particular risk posed by prescription drugs for people returning to work from injury, as they can lead to more damage when a person attempt their duties with dulled pain sensations.

Experts say while workplace drug testing is likely to increase, less expensive techniques such information or counselling would be as effective in some cases.

The NSW secretary of the Rail, Tram and Bus Union has told media outlets that the union supports a move to saliva, rather than urine testing.

“Mouth swab testing is safe, sure, instant and conforms with the National Rail Safety legislation and should replace the outdated practice of urine testing for NSW transport workers,” he said.