SIPTU members in Dublin Bus and Irish Rail are to ballot for industrial action in support of Bus Eireann workers.

It comes as the all-out strike continues for a fourth day.

The union says staff at Dublin Bus and Irish Rail believe that they are "next in the firing line" if Bus Eireann forces through wage cuts without union agreement.

At a meeting today, the Bus Eireann board today said it could not sign off company accounts for 2016, due to the dispute.

The company says it is on the verge of insolvency, and has urged staff to engage with management to agree a survival plan.

The board today considered a management plan to secure the future of the company, which includes measures to eliminate what Bus Éireann calls "grossly inefficient work practices".