A former senior News Limited journalist has described trying to write about human-induced climate change at The Australian newspaper as “torture” and has blamed the editor-in-chief for limiting coverage on the topic because he has “taken a political view”.

Asa Wahlquist mounted an off-the-cuff defence of environmental reporting on a panel at yesterday’s journalism educators conference in Sydney, explaining the difficulties of having stories published about climate change because of the attitude of and pressure from senior editors at the paper.

Her comments were quickly reported on Twitter, prompting editor-in-chief Chris Mitchell to threaten legal action against the author of the tweets and anyone else who published the “lie”.

As we go to press, a report in The Australian confirms that Mitchell will sue Julie Posetti for defamation. The paper reports that Posetti could not be reached for comment.

Mitchell told Crikey this morning that “any reading of The Oz’s editorials on climate change would make it clear that for several years the paper has accepted man-made climate change as fact”.

“It has supported market mechanisms to reduce carbon output for the best part of a decade,” he said. “What people do not like is that I publish people such as Bjorn Lomborg. I will continue to do so, but would suggest my environment writer, Graham Lloyd, who is a passionate environmentalist, gets a very good run in the paper.”

Wahlquist, the long-time science and rural affairs writer for The Australian, accused Mitchell of controlling coverage of climate change because he believes those who subscribe to the “eco-fascist line” that humans have induced climate change are “aiming to destroy everything he loves and values”.

Wahlquist has been a respected rural affairs journalist for more than 20 years, formerly working at the ABC and The Sydney Morning Herald. She won a Walkley Award and the coveted Peter Hunt Eureka Prize for her coverage of complex scientific stories. She joined The Australian 14 years ago, and joked yesterday she may have been the only person in the building who had a science degree. She resigned two months ago and now works as a freelancer.

Despite her qualifications, Wahlquist says she self-censored stories on the human causes of climate change fearing they would not be run. She described this as “professionally compromising” and “unbearable”.

Wahlquist noted the irony in Rupert Murdoch’s quest to reduce carbon emissions at his various News Limited companies around the world, while the editor-in-chief of one of his flagship newspapers appears to doubt that humans are responsible for global warming.

“The one bit of good news from this is that it shows that News Limited editors are independent,” she said.

Wahlquist told Crikey she was responding yesterday to claims from journalism academics that environmental reporters had failed to cover the issue fairly.

Posetti, a journalism academic at the University of Canberra, tweeted the comments during the conference and Mitchell tells Crikey today he will “vigorously” pursue action against her and “any repeat of the allegations that I have ever done any of the things alleged by the tweeter will meet similar action”. (Wahlquist herself admits some of the reported comments were taken out of context, though others in the forum agreed the comments were ambiguous.)

“My lawyers started work on this yesterday,” Mitchell said. “I am not one who believes new media should be exempt from the normal laws of the land … There is not protection from the law in repeating accurately allegations falsely made.”

Wahlquist told the panel she left The Oz due to the daily grind of news journalism: “When I started at The Australian 14 years ago it was as a features writer, but I wrote two features in the last year. You can’t cover this stuff [complex stories on topics like climate change] in news stories … I couldn’t do it any more, my health gave up. I tried to stay. I saw some value in staying because it was important.”

But, she said: “As a news writer you have no power with the way it is reported. Someone rewrites your copy. This happens more than you know.”

And asked whether alarmist predictions about the effects of global warming had made her job as a reporter at The Australian more difficult, she responded: “It doesn’t help, especially when you have an editor who is inclined to conspiracy theories.”