Some of the most high-profile liberal figures have joined together to encourage advertisers to boycott Twitter if Elon Musk brings in his promised policy of unfettered 'free speech.'

Twenty six NGOs and advocacy groups signed a letter expressing concern about the world's richest man's plan.

Musk himself responded to the letter asking who funded them: the answer being an assortment of 'dark money groups' like George Soros's Open Society Foundation; NGOs founded by former Clinton and Obama administration staffers; wealthy Democrat donors and their family foundations; labor unions; and the governments of European nations. 

'Elon Musk's takeover of Twitter will further toxify our information ecosystem and be a direct threat to public safety, especially among those already most vulnerable and marginalized,' they wrote.

They warned that advertising on Twitter would see their company 'risks association with a platform amplifying hate, extremism, health misinformation, and conspiracy theorists.' 

The authors continued: 'Under Musk's management, Twitter risks becoming a cesspool of misinformation, with your brand attached, polluting our information ecosystem in a time where trust in institutions and news media is already at an all-time low. 

'Your ad dollars can either fund Musk's vanity project or hold him to account. We call on you to demand Musk uphold these basic standards of community trust and safety, and to pull your advertising spending from Twitter if they are not.'