Relationships at work: what the law says 

In order to claim sex discrimination, your gender or your married or civil partnership must be the main reason for what happened to you (although it does not have to be the only reason). The Civil Partnership Act applies to same sex couples, and requires that they are treated in the workplace in the same way as married people.

You need to show that:

• but for your sex you would not have been treated in this way. You do this by comparing yourself with the treatment a member of the opposite sex receives, or is likely to receive, in similar circumstances
• but for your marriage you would not have been treated in this way. It is not unlawful under the Sex Discrimination Act for an employer to dismiss someone because they have married someone in the same organisation. Marriage discrimination is unlawful when an employer takes exception to married people in general (for example, refusing to employ any married people); it is not unlawful to discriminate against an employee because of the person they are married to
• a particular condition or requirement has been imposed by your employer which is discriminatory because it puts one sex, or married people, at a disadvantage and is not necessary. An example of indirect sex discrimination could be a policy, which states that in the event of a personal relationship, the lower graded employee is transferred. This could disadvantage women in an organisation where the lower grades are held by women, and the higher grades by men.

It is not unlawful under the Sex Discrimination Act to discriminate against someone because they are single.