Even before the electricity market is opened up, the competitors have clashed over the content of the Electricity Regulation Bill, which will govern the deregulated market and establish a new independent regulator for the sector.

Viridian, which plans to build a £300 million (€380 million) power station in Dublin with CRH, says the Bill, currently making its way through the Oireachtas, is "pro-ESB".

The company claims Section 13 of the Bill automatically gives the ESB the right to have its plants authorised by the Regulator, Mr Tom Reeves, whereas other operators will not automatically have their's authorised. They claim this means Mr Reeves will be "toothless" when it comes to dealing with the ESB, because no matter what the company does he will have to authorise its plants.

This contentious section, which is likely to be dealt with at committee stage of the Bill next Tuesday, is interpreted differently by the ESB.

The company says its plants have to be authorised because currently there is a serious power shortage in the State and the only company in a position to deal with it, in the short term, is the ESB.

It is currently preparing a site in Ringsend, Co Dublin, along with Statoil, for a £200 million gas-fired station. It expects this station to become operative before Viridian's station at Huntstown, Co Dublin, although both are currently subject to planning appeals.

The other vital issue is the classification of combined heat and power (CHP) plants in the Bill. These are plants which combust gas and air to generate electricity and heat, but unlike conventional production, retain the heat for re-use.

As the Bill currently stands CHP operators, like the property group, Treasury Holdings, might be able to offer their services to 100 per cent of customers, because the Bill classifies CHP as a "renewable" form of energy. The ESB and wind farm companies are opposed to this and say CHP is not renewable because it uses fossil fuels.