He said the decision to buy the credits also showed that the government had no interest in supporting renewable energy in Ireland.

O'Connor's comments come as Ireland ranked in the bottom half of a respected international survey of the most attractive countries for renewable energy investment.

Ireland came 12th of the 20 countries measured in Ernst & Young's Renewable Energy Country Attractiveness Index, behind countries such as Britain, the US, India and China. O'Connor, whose firm announced a $1.5bn wind farm development in Texas last week, said he agreed with the survey's findings.

"Ireland has become a very bad place to do business for all green technology, " he said. "Compared with the Bush government, we're hopeless."

O'Connor said it took 70 months on average to connect a wind farm to the national grid in Ireland, compared to 70 days for a fossil-fuel fired power station.

"It seems that the regulator here sees no value in wind even though its one of our greatest natural resources."

He also predicts that the government's decision to buy carbon credits to cover Ireland's rising emissions would cost far more than predicted.

"Their figures were predicated on Ireland emitting 3.6 million tonnes over its allowance and paying 15 per tonne for credits. I would have budgeted on 30 to 50 per tonne and we're now over five million tonnes over the allowance, which means the total bill could be as high as 1bn, " he said.

A spokesman for the Department of the Environment claimed O'Connor's figures were "wildly inaccurate". He said the budget for carbon credits had been set by independent consultants hired by the government.

A spokesman for the Department of Communications, Marine & Natural Resources defended Ireland's record in renewable energy.

"Far from lagging behind, we believe it is not an exaggeration to say that Ireland is one of the world leaders in growing the wind-powered sector allowing for market size, " the spokesman said.

He said the amount of energy generated by Irish wind farms had increased by 600% since 2003. But he added that energy regulators had to be cautious about adding wind farms to the national grid due to the need to ensure the stability of electricity supplies.

"For example, on 13 December, when Ireland's electricity demand reached its highest-ever peak at 5,742 MW, only 5MW of this figure was provided by wind energy, " he said.