The Taoiseach, Mr Ahern, this evening flatly rejected criticism over his Government's decision to increase car tax by 12 per cent.
Mr Ahern said the increase, which comes into effect next month, would fund the regional road building programme.
He said the increased revenue would in part also fund repair work on the many pot-holed roads across the country.
The Minister for the Environment, Mr Cullen, announced the increase this morning, saying the extra €67 million revenue would be invested in the non-national road network. The tax will affect all classes of vehicle.
It is the biggest increase in motor tax in ten years and the third since 1993. Mr Cullen said inflation had gone up by 33 per cent since the last increase, while motor tax had only risen by 12 per cent.
Annual motor tax for an average sized 1.3-litre to 1.4-litre family car will rise by around €35, while owners of a two-litre car will face an increase of over €75 per year.
"It's important to point out that car tax issue is the one item that is ring-fenced and goes directly into the local government and into the non-national roads," the Minister said on RTÉ's Morning Ireland.
But Labour's environment spokesman, Mr Eamon Gilmore, argued the rise was simply a new tax "on the ordinary PAYE workers" who have already been hit hard in Wednesday's Budget.
Mr Gilmore claimed the higher rate was stealth tax being introduced to compensate for Government cuts in local government funding.
"This is being increased because in the Book of Estimates earlier this year, the Government froze the amount of money the Exchequer is putting into the local government fund, which means an effective cutback of 5 per cent," he said.
"That money is now being made up by charging the motorist".
Economists said the motor tax rises, together with the budget changes, would further hinder the Government's efforts to keep down the rate of inflation which - at 4.6 per cent - is already the highest in the European Union.
Estimates before the move on the motoring tax were that the price rise rate could soar to around six per cent early next year.