There is no question of a hole in the ESB pension unless everyone in the company retires at the same time, the Minister for Public Expenditure and Reform has insisted.

Brendan Howlin said the company was "one of the most robust institutions in the State", and the dispute over how it dealt with its pension liabilities would not have any impact on the sale of power plants as part of the Government's disposal of State assets.

Mr Howlin said, however, he did not have responsibility for the ESB.

Sinn Féin deputy leader Mary Lou McDonald, who had asked about the implications for the sale of the company, rejected Mr Howlin’s assertion that he could not comment.

She told him that if he had responsibility for the sale of ESB assets then “the due diligence involved in this from your perspective must mean you’re been through this company like a dose of salts”.

She added: “It’s a bit hard to believe you’d miss the magnitude of the hole in the ESB pension fund.”

The Sinn Féin spokeswoman on public expenditure and reform said that in 2010 “on a solo run”, without the agreement of workers or unions, the ESB had changed its pension fund from defined benefit to defined contribution, shifting all liability for the deficit of €1.6 billion to the workers.

She said employees had since balloted for industrial action with the prospect of the first ESB strike in decades.

She asked if the Minister appreciated the situation where a semi-State company altered its balance sheet in this manner to affect its credit rating for borrowing on the international markets.

Mr Howlin warned she was making very serious charges about altering accounts, and she should deal with Minister for Communications, Energy and Natural Resources Pat Rabbitte.