SIPTU has said the Government can generate €125m extra for the exchequer next year through the earlier introduction of a new tax on high-value pensions.
During Wednesday's Budget, the Government confirmed it would claim 41% of the value of pension payments in excess of €60,000 per year.
That measure will not be introduced until 2014, as there are legal issues that must first be dealt with.
However, SIPTU's Jack O'Connor said Enda Kenny could expedite the process.
"What has to be done is to find ways of generating the money," he said. "In this Budget, here is a measure that has been announced (ie the 41% pension tax), and simply implementing it more rapidly would obviate the need for (many) cuts.
"It doesn’t change the budgetary arithmetic by one cent."