In submissions to the NSW parliamentary inquiry into coal seam gas, which has its first public hearing today in northern NSW, and to a federal government inquiry, Drew Hutton of the Lock the Gate alliance has taken verbatim three references to shale gas in US research documents and substituted the words ''coal seam methane'' each time.

Shale gas exploration has been criticised as having a greater environmental impact than coal seam gas exploration.

The changes by Lock the Gate follow recent statements by Mr Hutton warning about false claims being made about coal seam gas.

Mr Hutton said recently he wanted to ensure people were not "hoodwinked by phoney claims", even though the Cornell University study cited in the Lock the Gates submissions does not contain the information in the manner his group attributed to it.

The disclosure comes after the distribution of a letter to farmers detailing false claims about a non-existent company called Hummingbird Mining Consulting.

''The study that Lock the Gates drew its material from makes no mention of coal seam gas and is of no relevance to the Australian coal seam gas industry. Two parliamentary inquiries have been misled,'' said Belinda Robertson, the chief executive of the Australian Petroleum Production and Exploration Association.

"The anti-CSG campaign is sinking into farce. The circulation of a fake letter to land-holders aimed at generating fear and repeatedly making unsubstantiated claims is bad enough, but misrepresenting the work of others is a new low.

''What is particularly disappointing is the poor level of scrutiny being applied to the very groups calling for a fact-based discussion.''

Mr Hutton said the change to the shale gas reference was ''an honest mistake''. ''We've sent a message to the secretary to the [NSW parliamentary] committee,'' he said. No letter has been sent to the federal government inquiry on the matter.

Follow Environment on Twitter