Twitter's chief executive Jack Dorsey has admitted that permanently banning Donald Trump set a "dangerous precedent" for the power of tech firms and their bosses.

In a series of tweets, Mr Dorsey expressed his discomfort with the unprecedented ejection of a serving US President, which he described as a "failure" of the company's mission to "promote healthy conversation".

Twitter was the first major social network to suspend and then to permanently ban Mr Trump after he used its service to exult protesters who stormed the US legislature in an attempt to overturn his election defeat.

The company's move was rapidly mirrored by social networks, smartphone makers, payment firms, web hosts, email providers and even the high-end exercise bike maker Peloton, who each launched their own crackdowns on Mr Trump and his supporters.

Mr Dorsey stood by Twitter's decision, saying that it was right for the company, but criticised the herding behaviour of the tech industry as a whole as a long-term threat to freedom of speech.

He said: "Having to take these actions fragment the public conversation. They divide us. They limit the potential for clarification, redemption, and learning. And [it] sets a precedent I feel is dangerous: the power an individual or corporation has over a part of the global public conversation.

"The check and accountability on this power has always been the fact that a service like Twitter is one small part of the larger public conversation happening across the internet. If folks do not agree with our rules and enforcement, they can simply go to another internet service.

"This concept was challenged last week when a number of foundational internet tool providers also decided not to host what they found dangerous... this moment in time might call for this dynamic, but over the long term it will be destructive to the noble purpose and ideals of the open internet."

Mr Dorsey's warnings echoed those of tech critics and European leaders, who were alarmed by the ability of a handful of private companies to unilaterally de-platform their own country's head of state.

His statement also cut little mustard with US conservatives, who accused him of obfuscation and of applying different standards to Mr Trump than to rival leaders such as Iran's supreme leader.

At the same time, Twitter and other social networks have usually given special treatment to most politicians, allowing their accounts to remain online after statements that would get ordinary users banned.

Smaller fringe social networks such as Parler and Gab, both popular with Mr Trump's more extreme supporters, have also been cut off from the mainstream internet over claims that they have allowed their users to call for and organise violence without consequence.

Texas Attorney General Ken Paxton said that Big Tech had some explaining to do to assure him that the take-down of Parler wasn't a political hit job on a conservative social media upstart.

“The public deserves the truth about how these companies moderate and possibly eliminate speech they disagree with,” Paxton said, while announcing formal requests for information from Google, Apple, Amazon, Facebook and Twitter about their content moderation policies and practices.

Mr Dorsey has long seemed uncomfortable with his own company's power, launching a project called "Bluesky" to turn Twitter into an open, decentralised software standard similar to that of the World Wide Web or the TCP/IP protocols that power the internet.

On Wednesday he touted that initiative, along with the decentralised network of Bitcoin, as a potential answer to Big Tech's power, but it is unclear whether it will ever bear fruit.