Elon Musk has subpoenaed his friend and former Twitter chief executive Jack Dorsey as he tries to back out of his $44bn (£37bn) deal to buy the social media company, according to a court document.

The Tesla chief – the richest man in the world – announced his plan to buy Twitter in April, but is now battling to not buy it.

Mr Musk and Twitter are headed for a court trial showdown on 17 October that is expected to determine if Twitter can force the billionaire to go through with the purchase.

This month, the SpaceX founder sold $6.9bn (£5.7bn) of his Tesla shares as his tussle with Twitter continues.

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.

The subpoena on Mr Dorsey was served last week and asks him 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.