A. In principle, you can have an enforceable pay secrecy clause. The exception, however, relates to ‘relevant pay disclosures’ under Section 77.3 of the Equality Act 2010.
This is a disclosure made for the purpose of finding out whether there is a connection between pay and having or not having a particular protected characteristic. Therefore, if the pay disclosure is made with the possibility of pay discrimination in mind, then a pay secrecy clause will not be enforceable.
If you are thinking about including a pay secrecy clause in your contract of employment then you should think about carving out the circumstances in which employees are permitted to talk about their pay under the Equality Act.
If your employee was told clearly that their pay rise should be kept confidential and it was discussed for a reason other than trying to establish whether there was an equal pay issue, it may be possible to discipline that employee for failure to follow a reasonable instruction.
Of course, the employee could say that the disclosure was made with a view to finding out whether there was any connection between pay and a protected characteristic and it may be difficult for you to dispute this.