Some shops are selling fake urine and detox kits to help people beat workplace drugs tests.

QCARBO32 can be bought over-the-counter from stores such as Switched on Gardener - the garden chain at the centre of a nationwide drugs bust in April - and offers a 100 per cent guarantee pass rate, or your money back.

Users are advised to drink the bottle then "urinate frequently".

The same stores are also selling Quick Fix Plus - a synthetic urine product which has to be warmed before it is handed in as a sample.

The products can also be bought from other stores in Auckland, such as The Hempstore and Cosmic Corner.

When the Herald purchased QCARBO32 from Switched On Gardner in Glenfield and the synthetic urine from the New Lynn branch, no identification or proof of age was requested.

QCARBO32 costs $90 and Quick Fix Plus $75.

A salesman justified the prices by saying "it's better than losing your job".

Hempstore owner Chris Fowlie said his company sold the products to give people back their privacy.

"Random drug testing goes against the Bill of Rights and the Privacy Act, and violates the natural justice of presumption of innocence."

Paul Fitzmaurice, from the Government agency Environmental Science and Research, said the fake urine was difficult to distinguish from the real thing.

"It looks like normal urine and it has similar chemicals to normal urine."

He declined to reveal how the two could be told apart in case manufacturers modified the synthetic urine, but he said the off-the-shelf product did not smell like the real thing.

Drug Detection Agency spokesman Nick McLeay said the workplace drug test agency came across people trying to use drug-detox products, but he did not believe they worked.

Even if the detox products were successful, they could not be used for random testing, a test after an accident, or suspicion-of-use testing as they would not have time to work.

But the Herald spoke to one woman who said she had used the cleansing drink to pass a pre-employment drug test.

"It gave me my dream job, so it's amazing."

Michael Quinlan, director of Switched on Gardener, and Cosmic Corner owner Mark Caswell declined to comment.