LONDON — Elon Musk says his deal to buy Twitter can’t move forward unless the company shows public proof that less than 5 percent of the accounts on the social media platform are fake or spam.

Mr. Musk made the comment in a reply to another user on Twitter early Tuesday. He spent much of the previous day in a back-and-forth with Twitter’s chief executive, Parag Agrawal, who posted a series of tweets explaining his company’s effort to fight bots and how it has consistently estimated that less than 5 percent of Twitter accounts are fake.

In his tweet Tuesday, Mr. Musk said that “20% fake/spam accounts, while 4 times what Twitter claims, could be much higher. My offer was based on Twitter’s SEC filings being accurate.”

He added: “Yesterday, Twitter’s CEO publicly refused to show proof of 5%. This deal cannot move forward until he does.”

It’s Mr. Musk’s latest salvo over inauthentic accounts, a problem he has said he wants to rid Twitter of.

At a Miami technology conference Monday, Mr. Musk estimated that at least 20 percent of Twitter’s 229 million accounts are spam bots, a percentage he said was at the low end of his assessment, according to a Bloomberg News report.

The battle over spam accounts kicked off last week when Mr. Musk tweeted that the Twitter deal was on hold pending confirmation of the company’s estimates that they make up less than 5 percent of total users.

Also at the All In Summit, Mr. Musk gave the strongest hint yet that he would like to pay less for Twitter than the $44 billion offer he made last month.

He said a viable deal at a lower price would not be out of the question, according to the report by Bloomberg, which said it viewed a livestream video of the conference posted by a Twitter user.

Mr. Musk’s comments are likely to bolster theories from analysts that the billionaire either wants out of the deal or to buy the company at a cheaper price. His tweet Tuesday came in reply to one from a Tesla news site speculating that Mr. Musk “may be looking for a better Twitter deal as $44 billion seems too high.”

Mr. Musk made the offer to buy Twitter for $54.20 per share on April 14. Twitter shares have slid since then and are now down by just over 8 percent, to close at $37.39 on Monday.

To finance the acquisition, he has pledged some of his Tesla shares, but they have slumped by a third since the deal was announced.