Billionaire Elon Musk said Tuesday that his purchase of Twitter would not go ahead unless he was given assurances on the bots that he says plague the platform, further complicating his acrimonious bid for the social media giant.

The chief of SpaceX as well as Tesla, Musk is currently listed by Forbes as the world's wealthiest person, with a fortune of about $230 billion, much of it in Tesla stock.

Seen by his champions as an iconoclastic genius and by his critics as an erratic megalomaniac, Musk surprised many investors in April with news that he wanted to purchase Twitter.

But his $44 billion bid for Twitter is now "temporarily on hold," pending questions over the social media company's estimates of the number of fake accounts, or "bots."

"Yesterday, Twitter's CEO publicly refused to show proof of <5 per cent," tweeted Musk, who has almost 94 million followers on the social network.

"This deal cannot move forward until he does."

Twitter chief executive Parag Agrawal has said the platform suspends more than a half-million seemingly bogus accounts daily, usually before they are even seen, and locks millions more weekly that fail checks to make sure they are controlled by humans and not by software.

Internal measures show that fewer than five percent of accounts active on any given day at Twitter are spam, but that analysis can't be replicated externally due to the need to keep user data private, Agrawal contended.

Musk, who has said bots plague Twitter and that he would make getting rid of them a priority if he owned the platform, responded to that tweet by Agrawal with a poo emoji.

"So how do advertisers know what they're getting for their money?" Musk tweeted in a subsequent response about the need to prove Twitter users are real people.

"This is fundamental to the financial health of Twitter."

The process used to estimate how many accounts are bots has been shared with Musk, Agrawal insisted.

"It appears the spam/bot issue is cascading and clearly making the Twitter deal a confusing one," Wedbush analyst Dan Ives said in a note to investors.

"The bot issue at the end of the day was known by the New York City cab driver and feels more to us like the 'dog ate the homework' excuse to bail on the Twitter deal or talk down a lower price."

Musk has described his motivation as stemming from a desire to ensure freedom of speech on the platform and to boost monetization of a website that is massively influential but has struggled to attain profitable growth.

He has also said he favored lifting the ban on Donald Trump, who was kicked off the platform in January 2021 shortly after the former US president's efforts to overturn his election defeat led to the January 6 assault on the US Capitol.