A notorious hacking group claims to have “dirty laundry” on President Donald Trump and have threatened to publish it next week if one of the biggest cyber ransoms ever isn’t paid.

Cyber extortionists stole a trove of private data from US entertainment law firm last week Grubman Shire Meiselas & Sacks, before publishing documents relating to Lady Gaga and Madonna on the dark web.

In a blog post on Thursday on the dark web, hacker collective ‘REvil’ – who are holding thousands of the law firm ‘s documents hostage – said Mr Trump will be the next subject of a data dump.

“The next person we’ll be publishing is Donald Trump,” the blog post said.

“There’s an election race going on, and we found a ton of dirty laundry on time.”

The hackers added, “And to you voters, we can let you know that after such a publication, you certainly don’t want to see him as president. Well, let’s leave out the details. The deadline is one week.”

The White House has been contacted for comment.

In a statement provided to Variety through a representative, Grubman Shire Meiselas & Sacks said, “Our elections, our government and our personal information are under escalating attacks by foreign cyber criminals.

“Law firms are not immune from this malicious activity. Despite our substantial investment in state-of-the-art technology security, foreign cyber terrorists have hacked into our network and are demanding $US42 million ($A65 million) as ransom. We are working directly with federal law enforcement and continue to work around the clock with the world’s leading experts to address this situation.”

The statement continued, “The leaking of our clients’ documents is a despicable and illegal attack by these foreign cyber terrorists who make their living attempting to extort high-profile US companies, government entities, entertainers, politicians, and others.”

According to the firm, other organisations and companies including HBO, Goldman Sachs and the Department of Defence have been victims of similar cyber attacks.

It isn’t clear what info the hackers might have on Mr Trump or how it pertains to Grubman Shire Meiselas & Sacks, which is not known to have represented the US President in any legal matter.

-with agencies