Sources close to the Bus Éireann dispute said that an intervention by the Workplace Relations Commission early this week has not been ruled out.

However it is understood that any intervention would depend on two things.

First, there must be no resumption of last Friday's unofficial action, which temporarily halted services at Dublin Bus and Iarnród Éireann - causing serious transport chaos for hundreds of thousands of passengers.

Unions have denied that they played any role in orchestrating the unofficial pickets, and have consistently stated that they have no trade dispute with either Dublin Bus or Iarnród Éireann.

Second, ahead of any WRC intervention, any evaluation of the positions of management and unions would have to indicate that there has been sufficient movement to raise the possibility of a compromise or settlement.

The Workplace Relations Commission has consistently said that it remains available to assist if the parties request that they do so.

However, no such request has yet been made.

The strike has been continuing for 10 days, and is costing the company half a million euro per strike day - even after payroll savings are factored in.

The company lost €9.4m last year and further losses have been mounting at a rate of around €50,000 for each non-strike day this year.

Bus Éireann management has already warned that it could be insolvent by next month - and industrial observers have speculated that the company may be approaching a tipping point where examinership may become a necessity.

Meanwhile, Iarnród Éireann and Dublin Bus have jointly written to the National Bus and Rail Union informing them that they will be pursuing the union for costs incurred as a result of Friday's wildcat strike action.

The letter, which was sent to the NBRU on Friday, indicated that should orchestrated secondary picketing reoccur, the transport operators would take injunctive action.

Iarnród Éireann said that Friday's flash strike cost the company hundreds of thousands of euro. They will be making final calculations on the total cost early this week.

The NBRU expects to receive the letter from the two transport companies tomorrow.

Dermot O'Leary, General Secretary of the NBRU, said any allegations of wrongdoing levelled against the NBRU will be passed on to their legal people who will make a comprehensive assessment and respond accordingly.

Meanwhile, the General Secretary of the Irish Congress of Trade Unions has warned that the wildcat escalation of the Bus Éireann strike may delay a resolution of the dispute.

Speaking on RTÉ's Marian Finucane show, Patricia King described the unofficial stoppage which temporarily halted services at Iarnród Éireann and Dublin Bus as regrettable.

She said the escalation had delayed any third party intervention by the Workplace Relations Commission or the Labour Court, as they do not respond to that kind of pressure.

Ms King also said that the last thing the dispute needed was an intervention by the Minister for Transport Tourism and Sport Shane Ross in relation to the industrial relations issues.

However, she also noted that there were complex transport policy issues that needed to be addressed.

Minister of State Eoghan Murphy has said it is important Mr Ross does not intervene with the tax payer's cheque book to resolve the strike.

The Minister also condemned Friday's wild cat strike describing it as inexcusable.

Fianna Fáil's Michael McGrath called on Mr Ross to set up parallel talks to address the wider issues facing Bus Éireann.

Such a move would he said create confidence and pave the way for a resolution to the dispute.