The firm that will soon be sending out letters to some 4,000 Australians for alleged online copyright infringement is itself now being sued for infringing on the copyright of Godzilla in its upcoming film Colossal.

Soon after a Thursday court hearing, it is expected that iiNet and five other ISPs will be forced to hand over the details for 4,726 customers alleged to have downloaded the film Dallas Buyers Club to the film's owner, Voltage Pictures.

The company will need to get court approval before any letter is sent out to customers, but iiNet stated on Tuesday that it believes letters could be sent out as early as this week.

While Voltage Pictures has been strident in its own pursuit to protect its copyright, the company is now facing a lawsuit of its own over alleged infringement on the copyright of the iconic monster film character Godzilla.

Deadline has reported that Voltage Pictures has sent an email in early May to investors for a film called Colossal starring Anne Hathaway as a woman in Tokyo while it is under attack by Godzilla.

According to court documents filed this month in California, the owner of the copyright of Godzilla, Japan-based Toho is alleging that Voltage Pictures is "brazenly producing, advertising, and selling" an unauthorised Godzilla film.

The company slammed Voltage Pictures for its hypocritical approach to copyright law.

"That anyone would engage in such blatant infringement of another's intellectual property is wrong enough," Toho said in court documents.

"That defendants, who are known for zealously protecting their own copyrights, would do so is outrageous in the extreme.

The company stated that Voltage "purports to be a staunch advocate for the protection and enforcement of intellectual property rights" through its own copyright infringement suits for Dallas Buyers Club and The Hurt Locker.

In an interview in April, Voltage Pictures' vice president of royalties Michael Wickstrom said his company had deliberately taken a strong stance on copyright infringement.

"We're the first film maker to say enough is enough; if we don't change the business model, we will fail. We want to continue as a business, but when I see piracy rates in Australia above 50 percent, that's not a business model that can be sustained."

Toho alleges that in Voltage's own promotional material to investors, the company lifted an image of Godzilla from the authorised 2014 Godzilla film.

Similar to Voltage's own damages sought, Toho is asking for up to $150,000 in damages for each willful infringement of the Godzilla copyright by Voltage Pictures.

iiNet said on Tuesday it was looking to work with a legal firm to offer free legal services to customers sent letters for alleged infringement of Dallas Buyers Club.