UNITE:THE STATE'S second-largest union, Unite, is advocating a No vote in the Lisbon referendum.
Regional secretary Jimmy Kelly said yesterday that he would this week press the executive of the Irish Congress of Trade Unions to come out in favour of a No vote.
"The granting of legal status to the Charter of Fundamental Rights will not prevent the European Court of Justice making further rulings similar to the Laval case in Sweden, which is to the serious detriment of long-established workers' rights," he said.
Mr Kelly said his union's view that Lisbon was a poor treaty for workers was shared by the European Trade Union Congress.
He said a No vote would allow legislators time to include a "social progress" clause in a new treaty, offering genuine protection for workers across Europe.