With hundreds of National Grid employees still unpaid for work performed during Hurricane Sandy because of payroll system glitches, attorney general Martha Coakley on Monday fined the utility $270,000.

She called on National Grid to “resolve this matter immediately” or risk more fines.

“These workers provided a vital service during a storm that knocked out power for thousands of families across the eastern seaboard,” Coakley said in a statement. “The continued delays in paying workers their hard earned wages is unacceptable.”

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The problems stem from a new payroll system that National Grid began using shortly before Sandy hit the region in late October. That left the company little time to fix any glitches before it had to handle the complex pay and overtime issues created by mobilizing staff for a massive storm.

In the wake of Sandy, nearly 2,000 Massachusetts workers were paid late, at a lower paygrade, or for fewer hours than they had worked.

National Grid representative Jackie Barry said the utility apologized to its workers, and has been “aggressively addressing” the issue, and has continued to provide underpaid employees with supplemental checks and help to iron out delays in payments that are normally debited directly from their checks.

“We continue to focus on making things right for all our employees so they feel the respect and appreciation they deserve for jobs well done—especially those who worked tirelessly to restor power to customers affected by Superstorm Sandy,” Barry said.

On Monday, Dan Hurley, president of the Utility Workers Union of America Local 369, called the fine for National Grid a “step in the right direction,” but said the continuing glitches point to a “systematic failure” in the way the company operates, especially in regard to storms.

National Grid had hoped to correct the problems by mid-December, but was unable to meet that target as well as Coakley’s Dec. 21 deadline in order to avoid fines.