Drug use is reaching "worrying" levels in the Bay of Plenty as a number of companies struggle to fill job vacancies as potential employees fail standard drug tests.

According to the New Zealand Drug Detection Agency Ltd drug testing in the Bay of Plenty has increased in the forestry, tourism and farming sectors, with random testing results indicating methamphetamine is an area of concern.

A number of prospective employees at Rangiuru's AFFCO meatworks have failed a drug screen test.

Last year 6784 workplace drug tests were conducted in the Bay, with only eight per cent were "non-negative".

Bay of Plenty Federation Farmers president Rick Powdrell says it is standard for potential workers in the farming and agriculture industries to be tested for drugs.

He says the increase of drug use among potential employees in the farming industry is a real concern.

'There are cases of farm staff and drugs and we can't hide from it. Most employers have some form of addressing drug issues in their employment contract.”

Rick says drugs are the 'bane of society” and is causing some meat industries in the Bay, including AFFCO's Rangiuru plant, to be unable to fill job vacancies as potential workers continue to fail drug tests.

'In some of the other areas particularly in the meat companies they do have issues with the number of prospective employees turning up who don't pass drug tests.”

AFFCO Rangiuru plant manager Kevin Casey says all potential workers have to a pass pre-employment drug test.

'I ask them at the interview, can you pass a drug test? If you can't pass a drug test – no job.”

'I say that to every person and many of them will sit there and say ‘yeah I can pass the drug test' and they fail the drug test.

'At the end of the day I can't decide at an interview if a person smokes dope or not. But the bottom line is if I think they've got experience and they are what we're looking for then I give them the opportunity to pass the drug test and some of them do fail.”

Kevin says around 10 per cent of potential employees fail the drug test.

'Sometimes it is a bit annoying, you think you've got a readymade person who has got experience and then they fail it.”

Kevin says the company has never had an incident caused by a worker under the influence.

'It has been a problem in the past but I'm not aware of it here at Rangiuru.”

Cannabis continues to be the most frequent drug detected, showing up in 71 per cent of positive drug tests in 2012. Opiates including codeine, methamphetamine, amphetamine, cocaine and benzodiazepines were also detected.

The drug detection agency conducted more than 68,500 on-site drug screening tests in New Zealand last year.

Chief executive Chris Hilson says 95,000 tests have been undertaken this year so far.

Since October, 15 per cent of all workplace drug screening has been testing for synthetic cannabis with the figure expected to increase.

He says synthetic cannabis can be detected in a person's system for up to 102 days, which means some employees can still have drugs in their systems while on the job.