After a union-friendly city actuary underestimated the costs of early-retirement pension legislation to the tune of possibly several hundred million dollars, New York’s Independent Budget Office released its own study on the costs of the bill.

IBO calculates the cost of the bill to the city at $68.1 million for the first year alone, including pension and fringe benefit costs for employees. Previous cost estimates of the bill, which would allow certain public employees who had worked at least 25 years in the system to retire up to seven years earlier than the standard age of 62, have varied widely. The Bloomberg administration’s Office of Management and Budget said it would cost $200 million a year, and a former chief actuary for the city of New York, Jonathan Schwartz, said there would be no cost.

The communications director for the IBO, Doug Turetsky, said it was difficult to compare his organization’s figures directly with the long-run estimate of the OMB. But, he said, “Our estimate is below theirs certainly for the first year.”

In a statement yesterday, a spokesman for the mayor, Jason Post, said, “We disagree with the report’s methodology and believe that its findings are inaccurate.” The city maintains that its indefinite estimate of an eventual $200 million annual cost is correct.

The pension bill would apply to employees hired between 1973 and 1995. Because of the uncertainty surrounding the true costs, a sponsor of the bill, Assemblyman Ron Canestrari, said it would be tabled until next year.