ESB Networks is engaged in contingency planning ahead of tomorrow's 24-hour strike by network technicians belonging to a union that the company does not recognise.

However, as yet it is unclear what impact the stoppage is likely to have on customers, as the majority of network technicians belonging to recognised unions are not involved in the dispute.

The Independent Workers Union (IWU) has been engaged in a work-to-rule since Monday, whereby its members have refused to do overtime, or carry out stand by or call out duties.

The ESB has described disruption to date as "minimal".

The IWU claims to represent over 500 of the ESB's 1,200 network technicians, who carry out emergency repairs and other breakdown services - though other recognised unions estimate IWU membership at a maximum of 300 within the grade.

The IWU warns it will be placing pickets on all ESB networks premises around the country.

IWU Regional Secretary Gerry Corbett says the current dispute is over the company's failure to consult adequately on the outsourcing of certain work to contractors.

In a letter to the company's legal department, Mr Corbett says that the union is prepared to defer the planned strike if the company agrees to refer the dispute the Workplace Relations Commission (WRC) - something it has refused to do to date.

"On receipt of confirmation that the ESB are willing to refer these matters to the WRC conciliation service, we would be willing to defer the present industrial action pending the hearing of the issues in the conciliation process by an independent third party, the WRC," he writes.

Mr Corbett says the company has threatened to seek a High Court injunction to halt the strike, but adds: "We would also be of the opinion there is absolutely no reason whatsoever for this industrial/trade dispute to be deliberated upon by the High Court while the dispute resolution services of the State, the proper forum as identified in the1990 INDUSTRIAL RELATIONS ACT 1990 (CODE OF PRACTICE ON INFORMATION AND CONSULTATION) (DECLARATION) ORDER 2008 are readily available to both parties and not being availed of by the Employer."

The other network technician unions which are recognised by the ESB - Connect, SIPTU and Unite - have stressed that they are not in dispute with the company.

Unite has told members that they should work normally - and that whether they cross an IWU picket line would be a matter of individual conscience.

However, workers who do so will not be paid by the company and will not receive strike pay.

Some sources have claimed that this is essentially a union recognition dispute, though the IWU has categorically rejected that.

The IWU has said it apologises to anyone who may be negatively affected as a result of the "enforced" industrial action.

It justifies the action, saying: "It is also worth noting this dispute is not about money, that this dispute is about the failure of the Employer to partake in any meaningful discussions in relation to the continued outsourcing of our members work to outside third parties. (The continued privatisation of the ESB)".

The union rejects company suggestions that it has breached industrial relations procedures.