Elon Musk has threatened to walk away from his $44bn takeover of Twitter, accusing the social media company of "thwarting" his requests to learn more about its user base.
In a letter filed with regulators, Musk says he was entitled to do his own measurement of spam accounts.
The letter formalises a dispute that has simmered for weeks after Musk declared the deal "on hold" pending further information.
Twitter has defended its estimates.
But Musk believes spam and fake accounts represent a far greater share than the less than 5% of daily users that Twitter reports publicly.
The dispute has raised more doubts about the future of the takeover, which Twitter's board approved in April.
