Elon Musk has subpoenaed his friend and former Twitter chief executive Jack Dorsey as part of an effort to back out of his 44 billion dollar (£37 billion) agreement to acquire the company Mr Dorsey helped found, according to a court document.

Twitter and Tesla chief executive Mr Musk are heading for an October 17 trial in Delaware that should determine whether or not Twitter can force the billionaire to go through with the acquisition.

Twitter has subpoenaed a host of tech investors and entrepreneurs connected to Mr Musk, including prominent venture capitalist Marc Andreessen and David Sacks, the founding chief operating officer of PayPal.

Mr Musk has claimed that Twitter failed to provide adequate information about the number of fake, or “spam bot”, Twitter accounts, and that it has breached its obligations under the deal by firing top managers and laying off a significant number of employees.

Mr Musk’s team expects more information about the bot numbers to be revealed in the trial court discovery process, when both sides must hand over evidence.

Twitter argues that Mr Musk’s reasons for backing out are just a cover for buyer’s remorse.

Shortly after Mr Musk agreed to pay 38% above Twitter’s stock price, the stock market stumbled and shares of the electric car maker Tesla, where most of Mr Musk’s personal wealth resides, lost more than 100 billion dollars (£85 billion) of their value.

The subpoena was served last week.

It asks Mr Dorsey for documents and communications related to the acquisition, as well as information on the effect of fake or spam accounts on Twitter’s business and its measurement of daily active users.