Elon Musk has put his takeover of Twitter "temporarily on hold" until he gets more details about fake accounts on the social media platform.
Twitter said earlier this month that spam and fake accounts represent less than 5% of users.
But the Tesla and Space X founder confirmed he is now pausing his $44billion deal (around £36billion) until he gets further clarification about this figure.
Musk, 50, has said removing spam bots will be one of his main priorities once he is in charge of Twitter.
In a tweet, Musk said: "Twitter deal temporarily on hold pending details supporting calculation that spam/fake accounts do indeed represent less than 5% of users."
Shares in Twitter fell 20% in premarket trading this morning.
Musk's takeover of the social media giant was expected to be completed later this year after the Twitter board of directors unanimously approved his takeover deal.
Do you think Elon Musk will change Twitter for the better or worse? Let us know your thoughts in the comments below.
The world's richest man first offered to buy Twitter last month, just days after rejecting a seat on the company's board.
This would have prevented Musk from taking over the company.
Confirming the deal last month, Musk tweeted: "I hope that even my worst critics remain on Twitter, because that is what free speech means."
In a statement, he added: "Free speech is the bedrock of a functioning democracy, and Twitter is the digital town square where matters vital to the future of humanity are debated.
"I also want to make Twitter better than ever by enhancing the product with new features, making the algorithms open source to increase trust, defeating the spam bots, and authenticating all humans.
"Twitter has tremendous potential – I look forward to working with the company and the community of users to unlock it."
Musk, who is worth around $245billion, is a frequent user of Twitter and currently has more than 80 million followers on the social media platform.
He sold $8.5billion worth of Tesla stock last month to help fund his planned acquisition.
As well as tackling fake accounts, Musk also wants Twitter to become a platform for "free speech" and has vowed to reverse the bank of former US President Donald Trump.
He has also pondered introducing a "slight fee" for commercial or Government use but said casual users will still be able to use Twitter for free.
Musk wants to reduce the social media platform's reliance on advertising, as well.
