State regulators are asking officials at Northeast Utilities to justify “a number” of layoffs made by the company since it merged with Boston-based NStar in April, given earlier assurances by the utilities that they would handle most job eliminations through attrition.

“The Department is extremely concerned that there appears to be a major discrepancy between what the Joint Petitioners represented to the Department as their plan for personnel reductions and what [Northeast Utilities] is actually doing,” Ann G. Berwick, chair of the state Department of Public Utilities, wrote in a Nov. 6 letter to Northeast Utilities chief executive Thomas J. May.