An employer cannot treat employees worse because of:

• age
• disability
• gender reassignment
• marriage and civil partnership 
• pregnancy and maternity
• race/nationality
• religion
• sex
• sexual orientation

The law on discrimination and harassment is governed by the Equality Act 2010. According to it, an employee must prove that:

a. there was worse treatment, and
b. the worse treatment was due to one of the above reasons.

Therefore, it is not enough for an employee to accuse you of discrimination when he can only show that he was treated worse, he must also prove that the worse treatment was specifically caused by his nationality, age, disability etc.

However, you must remember that a discrimination case may have serious consequences for you, so never ignore such allegations.