SAN FRANCISCO: Twitter has sued a law firm that represented the micro-blogging platform as Elon Musk tried to back out of his deal to buy the platform for $44 billion.

Twitter's previous management hired the corporate law firm after Musk tried to terminate his agreement to acquire the company last year.

Wachtell, Lipton, Rosen & Katz, a top mergers and acquisitions firm, received a $90 million fee from Twitter, which according to the social network was "unjust enrichment", reports The New York Times.

Twitter now wants the fee to be returned. The lawsuit has been filed in San Francisco Superior Court by X Corp, Twitter's parent company.

The lawsuit said Wachtell Lipton took "funds from the company cash register while the keys were being handed over" to Musk, who owns X Corp.

According to documents submitted with the lawsuit, Twitter's board and executives approved the $90 million payment because the law firm had succeeded in making Musk abide by his agreement to buy the company.

Twitter had disputed other fees related to Musk's purchase of the company.

"An advisory firm, Innisfree M&A, sued Twitter for $1.9 million in February over what it said were unpaid bills. Joele Frank, a public relations firm, sued Twitter in May, arguing that it wasn’t paid about $830,498 for services rendered in the deal," the report said.