Businesses are being warned that cutting costs on drug tests now, could mean much bigger expenses down the track.
Some firms are carrying out in-house drug tests on workers, using low-cost do-it-yourself kits.
Drug Detection Agency chief Kirk Hardy says it's risky to use them especially if a firm goes on to suspend or dismiss someone.
"Any result from one of those on site tests must be confirmed in a laboratory.
"We're not seeing that."
Kirk Hardy says if the results prove to be false, employers could face costly lawsuits.
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