The ESB could push ahead with the closure of some of its older power plants by the end of this year.

It is due to shut and dispose of four facilities, the Marina in Cork, Poolbeg in Dublin, Tarbert in Kerry and Great Island in Wexford, by 2010, under the terms of a deal agreed last year with the State's Commission for Energy Regulation (CER).

However, the Amalgamated Transport and General Workers' Union (ATGWU) representative, Brendan Ogle, told The Irish Times yesterday that local management informed the 140 staff in Tarbert that the facility could be closed by this June. Recently 70 workers in Great Island were told its fate could be decided by October or November.

In response, the ESB said that as "part of the ongoing process involving the programme of closure and divestment of 1300mw of ESB plant, staff representatives in Tarbert were given an update at which a range of options for Tarbert station were outlined.

"Staff and unions are kept regularly informed of developments and no firm proposals were made in relation to timescales."

The ATGWU yesterday said it was time for unions to serve strike notice on the company, which is the sole supplier of power to the Republic's 1.7 million households. In November, 90 per cent of ESB workers voted in favour of striking to halt a Government plan to split the company and spin off the national grid to an independent body, Eirgrid.

Union representatives have signalled that they will not co-operate with the proposals to close and dispose of the four power plants if the Government presses ahead with its plan. The union wanted the ESB's board, which met yesterday, to give a commitment that it would oppose the break-up and to give its position following the meeting.

When this did not happen, the ATGWU issued a statement saying it was appalled that the board had "delayed on the issue" for 10 months. "We are obliged to convene a meeting with management and act on our members' mandate," the statement said.

Mr Ogle added that the ATGWU and the other ESB unions now had no choice but to issue strike notice.

The move would be unlikely to result in immediate work stoppages and blackouts, but could increase the risk of this happening.