Your employer has no automatic legal right to test you for drug or alcohol abuse and even if this is not provided for in your existing contract of employment, you can probably lawfully refuse. However, whether the employer can discipline or dismiss you for refusing will depend, among other factors, on the nature of your work.
Agreeing to be screened for drugs and drink is likely to be a requirement in jobs where safety is of paramount importance, for example working in public transport. It will often be a requirement indicated as an express contractual duty.
Where your employer keeps records of such tests it must comply with the data handling rules issued by the Information Commissioner – eg it will only be able to hold data for a limited time and in a secure environment.
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