I am paid less than someone of the opposite sex who is doing the same job as I am. Is this lawful?

It is unlawful for your employer to discriminate by paying you less than a member of the opposite sex, where both of you are doing like work, work rated as equivalent or work of equal value. This applies to all contractual benefits such as salary, overtime rates, bonus payments and other payments.

There are circumstances where unequal pay is permissible, called a genuine material difference, for example, the payment of a service increment, provided the difference is not based on the employee's sex.

Claims for equal pay should be made to an employment tribunal within six months of the date of the last complaint.