Thought Tidal couldn't get any more controversial? You were wrong.

Jay Z is preparing what the Nordic business press is calling a "giant lawsuit" against the former owners of the streaming service Tidal — and trying to claim back a sum in the "region of 100 million."

The rapper and business mogul has written to several of the former major shareholders in Tidal/WiMP owner Aspiro, accusing them of exaggerating how many subscribers the service had when his finance vehicle, Project Panther Bidco, bought the company at the start of last year.

If, as expected, that 100 million estimate is in Norwegian krone, it would amount to about $15 million.

Jay Z bought Tidal and its parent company Aspiro for 464 million Swedish krone ($57 million) in March last year.

According to the Swedish news service BreakIt — quoting an article in the Norwegian title Dagens Næringsliv ("Today's Business") — Aspiro's former major shareholders, including Schibsted and Verdane, have been contacted by reps for Tidal.

Jay Z reportedly claims that the figure his team were given for worldwide subscribers of the company in January 2015 — 503,000 — was misleading.

In addition, he claims that Wimp's business was in much worse condition than what was indicated in the statements he received at the time.

The Tidal launch party. Jamie McCarthy/Getty Images for Roc Nation

Perhaps that might partly explain why Jay Z told Billboard at the time of the sale that he would ensure fair artist payments "even if it means less profit for our bottom line," having bought a company that posted a $10 million loss in 2014.

Schibsted communications manager Anders Rikter told told Dagens Næringsliv that the company was "unsympathetic" to Jay Z's letter.

And Riker told BreakIt [translated]: "We want to point out that it was a publicly traded company that was acquired, [which means] transparency of financial reporting [was required]. Otherwise we have no comments."

Tidal this week announced that it had reached 3 million subscribers worldwide, also making the questionable claim that Kanye West's "The Life Of Pablo" had been streamed 250 million times on its service in its first 10 days.