Can a worker and union representative agree that the representative will answer all questions put to the worker at a disciplinary hearing?
No. Section 10 of the Employment Relations Act 1999 sets out what role a representative is permitted to play at a disciplinary hearing. The legal position is the same whether the representative is a trade union official or a work colleague. The representative is permitted to address the disciplinary hearing to: put the worker's case; sum up that case; and/or respond on the worker's behalf to any view expressed at the hearing. The representative is also permitted to confer with the worker during the disciplinary hearing.
However, the representative has no statutory right to answer questions on the worker's behalf, even if the worker wishes them to do so. The representative also has no right to address the disciplinary hearing if the employee indicates at the hearing that they do not wish the representative to do so. In addition, the representative may not use their rights to address the hearing and to confer with the worker in a way that prevents the employer explaining its case or any other person at the hearing making their contribution.
That said, in very limited cases, the employer should give consideration to permitting the representative to answer questions on behalf of the worker. Examples might include where English is not the worker's first language so the representative is also acting as an interpreter, or where the worker has a disability that precludes them from effective participation in the disciplinary hearing and it would therefore be a reasonable adjustment under the Equality Act 2010 to permit the representative to play a more active role.