Elon Musk has threatened to take legal action against antisemitism campaign group the Anti-Defamation League, accusing it of “trying to kill” his social media platform X.

Mr Musk said the ADL had “falsely accused” both him and the X platform of being antisemitic, causing a substantial drop in the social media platform’s advertising revenue as a result.

In a series of posts, the billionaire owner of the platform formerly known as Twitter said the company’s ad revenue in the US was down 60 per cent, which Mr Musk said was “primarily due to pressure on advertisers by the ADL”.

“To clear our platform’s name on the matter of antisemitism, it looks like we have no choice but to file a defamation lawsuit against the Anti-Defamation League … oh the irony!” Mr Musk said.

He accused the group of “destroying half the value of the company, so roughly $US22 billion” ($34 billion) and of making “unfounded accusations” that spark controversy and cause advertisers to pause working with X.

“Advertisers avoid controversy, so all that is needed for ADL to crush our US & European ad revenue is to make unfounded accusations. They have much less power in Asia, so our ad revenue there is still strong.

“This ‘controversy’ causes advertisers to ‘pause’, but that pause is permanent until ADL gives the green light, which they will not do without us agreeing to secretly suspend or shadowban any account they don’t like.

“To be super clear, I’m pro free speech, but against antisemitism of any kind,” Mr Musk added.

In response, the ADL said it did not comment on legal threats, but did comment on a campaign known as #BanTheADL that has recently circulated on the platform and Mr Musk has engaged with.

“Such insidious efforts don’t daunt us,” an ADL spokesperson said.

“Instead, they drive us to be unflinching in our commitment to fight hate in all its forms and ensure the safety of Jewish communities and other marginalised groups.”

Civil rights and other campaign groups have raised concerns about content on X since Mr Musk completed his takeover of the site last year. Many warned his avowed support of absolute free speech and the reinstatement of previously suspended accounts would allow more hateful content to spread on the platform.

Following Mr Musk’s takeover, some companies withdrew or reduced advertising on X over their concerns about these issues.