Is an employer required to consult with employees prior to giving notice of redundancies?
Yes, under the Trade Union and Labour Relations (Consolidation) Act 1992, when an employer is proposing to dismiss as redundant 20 or more employees at one establishment within 90 days or less, the employer has a duty to consult with the appropriate representatives of the employees who may be affected by the proposed dismissals, or who may be affected by the measures taken in connection with those dismissals. (In Usdaw and another v WW Realisation 1 Ltd (in liquidation) and others  IRLR 577 ECJ, the European Court of Justice confirmed that "establishment" means the entity to which the employees are assigned to carry out their duties, not the employer's organisation as a whole.)
The relevant definition of redundancy for the purpose of collective consultation is a "dismissal for a reason not related to the individual concerned". This includes the situation where an employer proposes to dismiss and re-engage employees who do not agree to a proposed variation of their contract.
Even where there is no duty to consult collectively, a redundancy dismissal will normally be unfair under the Employment Rights Act 1996 if there has been no or inadequate consultation with individuals.