It is understood that the letter from the ATGWU leadership was also copied to all members of Labour's national executive.

A spokesman for the Labour Party confirmed, in a short statement, that the letter had been received on Friday afternoon and said it would be replied to "in due course". In the statement, the spokesman said he believed that the vast majority of the public, including most trade-union members, would "share the view expressed by Pat Rabbitte that to make an initial response of a threat of industrial action in response to this issue, which could lead to blackouts in the ESB, was irresponsible and over the top".

He added: "We hope that wiser counsel will prevail and, in this regard, we welcome the more restrained/moderate approach expressed by trade-union leaders following their meeting with Noel Dempsey during the week."

Rabbitte's comments on Ogle caused a stir in union and Labour party circles. A group of Labour party members contacted the Sunday Tribune last week to express "outrage" at the attack, which they claimed was a "cheap publicity stunt" that was damaging to the Labour Party's position.

"Pat Rabbitte ought to spend less time attacking members of the Labour movement and more time attacking the government. The Labour position on the government's plans for the ESB was spelt out loud and clear by the party spokesperson Tommy Broughan and there ought to be unity behind this position, " party activist Paul Dillon said.

Another activist, Enda Duffy, said Rabbitte's comments were based on a "false understanding" of ESB's industrial situation. "Rabbitte accused Brendan Ogle of issuing an 'apparent threat' regarding blackouts.

"However, the possibility of industrial action was raised in a joint statement by six unions representing workers in the ESB."

Labour party and ATGWU member Chris Bond said the ATGWU was an affiliated member of the Labour Party and "the least our union and its representatives deserves is honest treatment and a bit of respect from the Labour Party leadership".