Sources have also indicated that two major electricity players . . . E.ON, one of Europe's largest energy companies, and Northern Irish electricity firm Viridian . . . are interested in acquiring the stations, Tarbert in Co Kerry, Marina Steam Turbine in Co Cork, Great Island in Co Wexford and the thermal units at Poolbeg in Dublin city.

It is understood the ESB board decided to approve the closure of the plants rather than selling them because a sale would have raised complex financial and political issues over staff obligations for the company.

"It does not mean they won't sell them if someone came to them with the right offer, " said an ESB source.

The source added that the ESB had decided not to approach bidders because there was an awareness in the energy business that the plants were available.

According to sources, German energy giant E.ON is particularly interested in the four plants, which represent around 20% of Ireland's electricity capacity.

The company's strategy is focused on large, high-profile acquisitions and sources said E.ON believed the plants represented an excellent opportunity instantly to become the secondlargest player in Ireland.

Meanwhile, a Viridian spokesman said it would be "interested in looking at any opportunity in the Irish market". He refused to say whether its plans involved the four stations. Sources said, however, that the company would be interested in acquiring the stations as going concerns. Viridian is understood to believe there is scope to improve efficiency at the plants.

However, any sale is likely to meet fierce resistance from the ESB's unions, with Amicus national officer Jerry Shanahan stating that his union opposed "any sale of ESB assets that enhances the business positions of competitors".

Shanahan also said no rival electricity company would be interested in the plants because it was impossible to make a profit from them. He said, however, that it was unlikely that closure or sale of the stations would lead to an industrial dispute at the ESB.

THE Commission for Energy Regulation (CER) has said it would consider delaying the closure of the four ESB power plants earmarked for decommissioning by 2010 last week if security of supply concerns made it necessary.

"If the plants are needed come 2009 or 2010, we're not going to shut them down for the sake of it. We have to take a pragmatic approach to this, " said a CER spokesman.

The ESB's trade unions have claimed that the closure of the plants will lead to significant security of supply issues because not enough new plants are planned to replace them.

The total output of the four plants that are set to close is 1,300MW, whereas the three new plants due to open by then have a combined output of 1,291MW, at a time when energy consumption is due to grow by about 4% a year.