Greenpeace has used the AGL logo in an online advertising campaign featuring the slogan "AGL - Australia's Greatest Liability".

The campaign describes the company as "Australia's biggest corporate climate polluter".

AGL owns three coal-fired power plants, Loy Yang A in Victoria and Liddell and Bayswater in New South Wales.

The Greenpeace ads were run online in the business sections of the Australian Financial Review and The Guardian.

At an initial hearing in the federal court in Sydney on Friday, AGL asked for a temporary injunction to stop Greenpeace using its logo, claiming it has breached copyright laws and infringed on its trademark.

The injunction has not been granted.

AGL's case is being run by one of Australia's leading intellectual property silks, John Hennessy SC.

He said the environmental campaigners could make their point without resorting to the use of the company's logo, according to a transcript of the hearing obtained by AAP.

"We will suffer irreparable harm if Greenpeace continues to use it for a purpose which is almost self-evidently harmful to AGL," he said.

Mr Hennessy added it would be very difficult to quantify what the damages might be if Greenpeace is able to continue using the logo.

The environment group's defence so far argues the AGL trademark is not being used in the course of trade, and was instead used as "part of a parody or satire".

Greenpeace Australia Pacific's general counsel Katrina Bullock told AAP the case will be important for campaigns run by charities in future.

"From a campaign perspective their response is a bit silly, and it's a weak legal case," she said.

The company has been contacted for comment on the case, which will return to court on Tuesday.

Australian Associated Press