Good Lawyer Guide's response

First of all, check the employee’s employment contract to see if there are any terms covering this type of situation. You may find that you can dismiss them on the spot if you have evidence of drug taking or they admit it. Also check your company’s staff handbook and rules so that if action has to be taken, you follow the correct procedures. You would not want to run the risk of a claim for unfair dismissal for failing to follow procedures.

It is very important to remember that the actual use of controlled drugs is a criminal offence. And more importantly as an employer, you will be committing a criminal offence if you know that illegal drugs are being used in the workplace. This means you must take decisive action if you have proof that drugs are being used. Without firm evidence of drug taking talk to your employee and offer help and support if necessary, and warn of the dangers both to his or health health and work performance, and the risk of being sacked if caught.

Finally, be careful before considering drug testing employees (unless it is a safety critical job) because this could breach human rights legislation.