The House of Commons Members’ HR Service has produced a Best Practice Guide to Grievances.

This best practice guide aims to enable Members and their HR proxies to respond to and investigate grievances fairly, consistently and effectively.

You can find the guide here: https://intranet.parliament.uk/images/intranet/Employment/Best%20Practice%20Guide%20-%20Grievance%20v1.pdf

This is one of a series of guides, and you can find the other guides here: https://intranet.parliament.uk/employment/house-of-commons-members/members-hr-advice-service/employing-new-staff/advice-on-employing-new-staff/