The world's richest man, who revealed last Friday that the takeover was "on hold" over the issue, said his offer to buy the company was based on filings by Twitter to the US markets regulator SEC (Securities and Exchange Commission).

Twitter estimates that the number of spam/fake accounts represent less than 5% of users but has admitted a constant battle to eliminate them.

They include so-called bots - automated accounts which have the potential to ply the platform with spam and potentially harmful activity.

They are programmed to perform multiple tasks like a human user, including things like retweeting posts.

It sounds harmless enough except for the fact bots across social media are blamed for influencing elections, conducting misinformation campaigns and terrorising individuals or groups.

The billionaire suspects fake accounts make up at least 20% of users - damaging the landscape for advertisers.

He wrote on Twitter early on Tuesday: "My offer was based on Twitter's SEC filings being accurate. Yesterday, Twitter's CEO publicly refused to show proof of

Musk appears to be using the issue as a way to force down the agreed price for the takeover - with Twitter's shares suffering amid the acrimony being played out in public.

He told a conference in Miami on Monday: "You can't pay the same price for something that is much worse than they claimed.

"The more questions I ask, the more my concerns grow.

"They claim that they've got this complex methodology that only they can understand... It can't be some deep mystery that is, like, more complex than the human soul or something like that."

Twitter CEO Parag Agrawal said that internal estimates showed fake accounts for the last four quarters were "well under 5%".

He has argued that the figure could not be reproduced externally given the need to use both public and private information to determine whether an account is spam.

Musk responded to Agrawal's defence of the company's methodology with a poop emoji.

"So how do advertisers know what they're getting for their money? This is fundamental to the financial health of Twitter," Musk wrote.

Twitter's stock closed on Monday at $39.39 per share - well below the $54.20 Musk has agreed to pay.

The shares are now below the level seen in early April when Musk first revealed his Twitter stake.