AUGUSTA – Gov. Angus King on Tuesday vetoed a measure to provide unemployment benefits to part-time workers. Supporters denounced his decision and promised a fight when lawmakers return next week.

“LD 1258 proposes to use a one-time infusion of federal funds into the trust fund to cover ongoing benefit expansion,” King wrote in his veto message. “While this would avoid an immediate unemployment tax increase, such an increase would be necessary at some future date.”

The bill was approved by narrow margins in both the House and Senate. A two-thirds vote in each chamber would be required to override the veto.

Tucked into the economic stimulus legislation signed by President Bush in February was a provision that gives Maine $32.5 million as its share of the surplus in the federal Unemployment Trust Fund. The legislation King has vetoed would use that money to pay for the new benefits for several years.

“We are very disappointed with the governor’s action,” said Chris Hastedt of the Maine Equal Justice Project, an Augusta-based group that advocates for people with low incomes. “This legislation addressed a serious inequity in the unemployment system and it would not cost employers.”

Laura Fortman, executive director of the Maine Woman’s Lobby, said King’s veto, if sustained, would have a disproportionate impact on poor women.

“When you look at the numbers, 70 percent of these part-time workers are women,” she said. “The governor’s decision is very disappointing.”

Technically, part-time workers in Maine are currently eligible for benefits, but they must seek full-time work in order to get the benefits. The measure would have changed that requirement so a part-time worker who is laid off could get benefits while looking for another part-time job.

“This [legislation] would have started to address the changing nature of the workforce,” Hastedt said. “There are far too may workers not covered by the unemployment system.”

Experts say about a third of the more that 600,000 Mainers in the work force are working part-time jobs and another 10 percent are self-employed and not covered by the unemployment system.

In his veto message, King did not address the concerns of supporters. He said that while the trust fund is in good shape, it may not be in the future when the federal funds run out.

“I am not able to support this legislation and view this expansion as another burden on Maine employers,” he wrote.

The unemployment insurance program is a federal and state partnership that pays benefits to unemployed workers who have lost jobs through no fault of their own. Benefits are paid through payroll taxes assessed on employers, and provide partial, temporary replacement of lost wages. States set their own eligibility and benefit levels with federal guidelines.