A leading defender of climate change admitted tricking the libertarian Heartland Institute into turning over confidential documents detailing its plans to discredit the teaching of science to school children in last week’s sensational expose.

In the latest revelation, Peter Gleick, a water scientist and president of the Pacific Institute who has been active in the climate wars, apologised on Monday for using a false name to obtain materials from Heartland, a Chicago-based think tank with a core mission of dismissing climate change.

“My judgment was blinded by my frustration with the ongoing efforts - often anonymous, well-funded and co-ordinated - to attack climate science,” Gleick wrote in a piece for Huffington Post.

The admission - nearly a week after Heartland’s financial plans and donors’ list was put online - looked set to further inflame the climate wars, in which a network of fossil fuel interests, rightwing think tanks and politicians have been working to block action on climate change.

In a sign of combat to come, Gleick has taken on a top Democratic operative and crisis manager, Chris Lehane. Lehane, who worked in the Clinton White House is credited for exposing the rightwing forces arrayed against the Democratic president. He was Al Gore’s press secretary during his 2000 run for the White House.

As one environmental campaigner said: “Now it’s gone nuclear.”

Heartland’s president Joseph Bast said the unauthorised release of confidential documents - and a two-page memo it has condemned as a fake - had caused permanent damage to its reputation.

“A mere apology is not enough to undo the damage,” he said in a statement.

Bast also disputed Gleick’s account that he had received the first document - the faked two-page memo - from an anonymous source.

He said Heartland was consulting legal experts.

In the piece, Gleick made the odd claim that he carried out the hoax on Heartland as a means of verifying the authenticity of a document that appeared to set out the think tank’s climate strategy. Heartland declared the two-page memo a fake.

“At the beginning of 2012, I received an anonymous document in the mail describing what appeared to be details of the Heartland Institute’s climate programme strategy. It contained information about their funders and the Institute’s apparent efforts to muddy public understanding about climate science and policy. I do not know the source of that original document but assumed it was sent to me because of my past exchanges with Heartland and because I was named in it,” Gleick wrote.

“Given the potential impact however, I attempted to confirm the accuracy of the information in this document. In an effort to do so, and in a serious lapse of my own and professional judgment and ethics, I solicited and received additional materials directly from the Heartland Institute under someone else’s name. The materials the Heartland Institute sent to me confirmed many of the facts in the original document, including especially their 2012 fundraising strategy and budget. I forwarded, anonymously, the documents I had received to a set of journalists and experts working on climate issues.”

Gleick’s admission was seen by some as crossing a new line in the increasingly vitriolic debate between scientists, campaigners, businesses and politicians who want action on climate change and a small but well-funded group of those who deny the existence of man-made climate change.

Some were dismayed the revelations. Others suggested that Heartland had got what it deserved - given its support for efforts to discredit science.

“Heartland has been subverting well-understood science for years,” wrote Scott Mandia, co-founder of the climate science rapid response team. “They also subvert the education of our school children by trying to ;’teach the controversy’ where none exists.”

He went on: “Peter Gleick, a scientist who is also a journalist just used the same tricks that any investigative reporter uses to uncover the truth. He is the hero and Heartland remains the villain. He will have many people lining up to support him.”

Gleick, a well regarded water scientist, has been an important figure in the increasingly heated climate wars, and has sparred often in print against Heartland and others who deny the existence of climate change, such as the Republican Senator Jim Inhofe.

Last month, Gleick signed on with a new initiative to defend the teaching of climate change.

He offered that bruising experience on Monday as an explanation for his actions.

But Gleick does not appear to have experienced immediate remorse. He did not move to claim the ruse until there was already feverish online speculation about his involvement. He responded to a request by The Guardian for comment last Wednesday by saying he did not wish to comment.

Those actions may have undercut an entire career, the journalist Andrew Revkin wrote.

“Gleick’s use of deception in pursuit of his cause after years of calling out climate deception has destroyed his credibility and harmed others,” he wrote.

“The broader tragedy is that his decision to go to such extremes in his fight with Heartland has greatly set back any prospects of the country having the “rational public debate” that he wrote - correctly - is so desperately needed.”

Kert Davies, the research director of Greenpeace USA, said it would be unfortunate if the row over Gleick and his methods to obtain the documents distracted from Heartland’s work to block climate action.

“There are a lot of people involved with Heartland’s multimillion dollar climate denial machine who want to change the subject to anything else.”