ESB workers are threatening to act on their strike threat next month unless the State company's board assures them that the power group will not be split.

ESB management met unions yesterday to discuss a recent vote by members to strike in a bid to stop the Government from spinning off its electricity transmission grid to a different State body, Eirgrid.

The unions sought assurances that the company will not be split, that it will not dispose of a number of power station sites and that the ESB will continue to be run as a "vertically integrated" group, meaning it will generate, transmit and distribute power.

Brendan Ogle of the Amalgamated Transport and General Workers' Union told The Irish Times yesterday that workers want the assurances from both the management and the board, following the latter's meeting in January.

He added that it the board is not prepared to give the assurances, the unions have a strike ballot and are prepared to act on it."The board are going to have to decide if they are going to implement the plan. They cannot continue to play both sides."

Mr Ogle argued that the plan to split the company, contained in a Government White Paper published last March, was contrary to two agreements signed between the ESB and its workers following restructuring in 1996 and 2000.

A company statement said that that the group of unions raised serious concerns about "certain aspects" of the White Paper, and that both sides had agreed to meet again next month.

Sources confirmed that the unions had sought assurances about the company's future. The board is due to meet today.

The Government says that the plan to spin off the national grid is designed to encourage competition and further investment in the Republic's electricity market.

The ESB's rivals, such as Viridian-owned Energia, also use the grid to transmit the power they produce and say that there is a conflict of interest in allowing the State company to act both as an electricity generator and distributor.

The previous government drew up the White Paper, but it has the support of the current Minister for Energy, Eamon Ryan. He recently appointed former AIB chairman Lochlann Quinn to the same position at the ESB. He is due to take up his new role following next month's board meeting.