WASHINGTON (Reuters) - Environmental group the Sierra Club sued the U.S. Energy Department on Monday in hopes of forcing it to reveal the groups it has consulted in conducting an eagerly awaited study on the electricity grid.

It was the latest push-back on the department’s study from backers of renewable energy such as wind and solar power who fear it could be used by the Trump administration to form policies that could slow growth in the industry.

Energy Secretary Rick Perry, who commissioned the 60-day study in April, ordered his department to see whether “regulatory burdens” by other administrations including former president Barack Obama’s had forced the premature retirements of so-called baseload power plants, fired by nuclear and coal. Perry said those policies potentially put at risk the reliability and security of the national power grid.

The Sierra Club, in the suit filed Monday in the U.S. District Court for the Northern District of California, said the department had ignored a Freedom of Information Act request it filed in May. That request sought the release of communications between staff and outside groups it had consulted, in the belief that the Energy Department had mostly relied on fossil fuel backers.

“We want to make sure that when this study is finally released, that the public and policy makers fully understand how it went about doing it, who they were influenced by, and whose views they did not take into consideration,” said Casey Roberts, a Sierra Club lawyer.

The Energy Department did not immediately respond to a request for comment. It had initially said the report would be released in July, but the release has been delayed. A draft of the study, conducted by a contractor who included contributions from staff across the department, said that intermittent renewable power has not harmed the grid, was leaked to the media last month.

But an energy department spokeswoman said then that the draft was “outdated” and had not been reviewed by political or career staff, leading Sierra Club and others to believe the final draft could favor coal and nuclear.

Several lawmakers with strong renewable power output in their states have said that the Energy Department had already completed long-term studies of renewable power’s impact on the grid that concluded there has been no harm. Senator Chuck Grassley, a Republican from Iowa, raised concerns in a letter sent to Perry in May that the secretary had commissioned a study that appeared “geared to undermine” the wind energy industry.