In response to the unions' release, the HSE said that Bernard Gloster has asked the HSE's National Employee Relations Service to request the Work Relations Commission to intervene in the threatened industrial action.

Unite said withholding pay when employees are unable to work could be considered an unauthorised deduction from wages, and therefore unlawful.

Siptu and Fórsa agreed pay rises of 12 per cent with Aer Lingus in recent years, but the deals include a clause where they can go back to the airline if another group of workers secures a better deal

The first walkout in the dispute over pay will take place on Thursday February 1.

Public sector workers are taking part in walk-outs in a dispute over a pay award.

The walkouts are expected to be the largest strike in the North in recent history