1. The employee who raises a grievance when faced with disciplinary proceedings.
The ACAS Code states that: “Where an employee raises a grievance during a disciplinary process the disciplinary process may be temporarily suspended in order to deal with the grievance. Where the grievance and disciplinary cases are related it may be appropriate to deal with both issues concurrently”
Therefore the ACAS Code allows for both options. If the grievance and disciplinary are related it is advisable to deal with them concurrently. If they are unrelated then it is nearly always advisable to pause the disciplinary proceedings and deal with the grievance before resuming the disciplinary. (One exception may be when the disciplinary process is about to be concluded at the point the grievance is raised. In that case the employer could opt to finalise the disciplinary and then deal with the grievance or still pause the disciplinary process to deal with the grievance first.)
An employer should decide which option is appropriate; and that will very much depend on the facts and circumstances.
If an employer took no action at all to investigate a grievance raised during a disciplinary process, it is likely to be a breach of the ACAS Code which will be taken into account when assessing compensation (i.e. it could result in an uplift if the employee brings a claim that is successful).