BOSTON (AP) — Gov. Deval Patrick’s administration has asked Massachusetts utility regulators to hold up on approval of Connecticut-based Northeast Utilities’ proposed $4.73 billion purchase of Boston-based NStar.

The state Department of Energy Resources has asked the Department of Public Utilities not to make a decision until NStar completes a formal review of its rates.

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WBZ NewsRadio 1030’s Kim Tunnicliffe reports

That delay could result in approval being put off until late next year, a delay the two companies say could jeopardize the deal.

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State energy officials say the companies have failed to provide sufficient detail about the environmental and financial benefits of the proposed merger.

Officials of Northeast Utilities and NStar have said the merger, creating the largest utility in New England, would not stifle competition or increase rates but would result in savings to customers.

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