Eversource Energy, a New England utility and supplier of natural gas, has threatened legal action against the Environmental Defense Fund (EDF) if the organization does not back away from citing a study that accuses the company of artificially limiting gas supplies to the region to benefit from price spikes.

Eversource (NYSE: ES) fired off a cease-and-desist letter on Dec. 11, saying EDF has “repeatedly published assertions drawn from the so-called study ... that are unsupported by fact. In particular, your repeated public assertions that Eversource has intentionally withheld gas pipeline capacity from the wholesale power market in order to profit from higher electricity prices are patently false.”

In an e-mail responding to a request for comment from Hart Energy, EDF spokesman Jon Coifman acknowledged that the organization had received the letter and referred it to counsel for review.

“We stand by the analysis and reject this obvious attempt to intimidate and chill legitimate public inquiry,” Coifman wrote in the e-mail.

Among the assertions that Eversource objected to was a Nov. 16 op-ed by Fred Krupp, president of EDF, in the Wall Street Journal and comments made by N. Jonathan Peress, the organization’s senior director of energy market policy, during a panel discussion at the S&P Global Platts Pipeline Development and Expansion conference in mid-November in Houston.

In the letter from Gregory B. Butler, Eversource’s executive vice president and general counsel, the company maintained that it adheres to state regulatory mandates that ensure customers in Massachusetts and Connecticut have uninterrupted sufficient natural gas even on the coldest days.

“The statements in the EDF Report that you have repeated ignore the most elementary principles of utility regulation and the regulation of utility fuel supply,” Butler wrote.

The study, “Vertical Market Power in Interconnected Natural Gas and Electricity Markets,” was authored by Levi Marks of the University of California-Santa Barbara; Charles F. Mason of the University of Wyoming; Kristina Mohlin of the EDF; and Matthew Zaragoza-Watkins of Vanderbilt University.

The authors contend that “severe, concurrent price spikes” that have plagued New England natural gas customers, especially during the “Polar Vortex” winter of 2013-2014, were aggravated by two companies in particular.

“Limited pipeline capacity is indeed partly responsible for these extreme prices,” they wrote. “But we also find strong evidence that two firms that held significant shares of the contracts to flow gas on the Algonquin Gas Transmission Pipeline – one of the two major pipelines serving New England – regularly restricted capacity to the region by scheduling deliveries without actually flowing gas.”

The authors identify Eversource and Avangrid Inc. (NYSE: AGR) as the firms and base their findings on an analysis of three years of scheduling data for the pipeline. Their conclusion was that the withholding of pipeline capacity cost electricity ratepayers $3.6 billion.

Joseph Markman can be reached at jmarkman@hartenergy.com and @JHMarkman.