Transport Minister Paschal Donohoe has said that he cannot use any of the proceeds from the sale of the State's stake in Aer Lingus for the deferred pension scheme.
Speaking in the Dáil, Sinn Féin's Dessie Ellis called for some of the expected €335m from the sale to be used to protect the pensions of former workers.
But Minister Donohoe says European accounting rules prevent him doing this.
"Because of the rules that are in place, we are not able to use any funding," he said.
"Were it to happen, if the stake was to be sold - for current Government expenditure, it can only be used for commercial purposes."