Twitter founder Jack Dorsey has welcomed Elon Musk’s £34.5 billion takeover of his company as others questioned the future safety of the platform and some users threaten to leave.

The Tesla and SpaceX chief executive has reached an agreement to buy the social media platform for 54.20 US dollars (£42.20) per share – about 44 billion dollars (£34.5 billion).

Mr Dorsey, who founded Twitter in 2006, gave his blessing to the takeover in a series of tweets – hailing the decision to let Mr Musk take the social media platform into private ownership and away from the ad model and Wall Street, but others have raised concerns about online safety on Twitter going forward given Mr Musk’s belief in absolute free speech.

Online safety campaigners said this could have a “chilling effect” on child safety even after new regulation is introduced to the sector, and some users have announced plans to leave the site because of fears over an increase in potentially harmful speech.

Critics of the takeover have said Mr Musk’s stance as a “free speech absolutist” could mean Twitter’s content moderation rules are loosened and more controversial content will be allowed on the site.

Mr Musk has previously said he wanted to buy Twitter because he did not believe it was properly serving the purpose of being a platform for free speech and too many people were being censored.

Andy Burrows, the head of child safety online policy at children’s charity the NSPCC said urgent clarity was needed over what approach a Musk-led Twitter would take to tackling online abuse.

“There’s a huge difference in outcomes between a platform that tackles online sexual abuse versus meeting basic legal requirements,” he wrote in a tweet.

“It’s too early to draw conclusions but the headwinds point to a chilling effect. Proper regulatory guardrails have never felt more important.

“The tension between libertarian points of view & tackling illegal behaviour isn’t new, but is pressing.

“Would Twitter still scan for child abuse in DMs (direct messages)? If the Online Safety Bill prevents Ofcom from proactively requiring it, where are we?”

But former Twitter chief executive Mr Dorsey said the sale to Musk was the right move.

“In principle, I don’t believe anyone should own or run Twitter,” Mr Dorsey said.

“It wants to be a public good at a protocol level, not a company.

“Solving for the problem of it being a company however, Elon is the singular solution I trust. I trust his mission to extend the light of consciousness.”

Mr Dorsey added that he believes this is “the right path” for his company.

Elsewhere, The Good Place actress and campaigner, Jameela Jamil, was among those who said they would leave the site in the wake of the deal.

“Ah he got twitter. I would like this to be my what lies here as my last tweet,” she wrote, alongside pictures of a dog.

“I fear this free speech bid is going to help this hell platform reach its final form of totally lawless hate, bigotry, and misogyny. Best of luck.”

The names of other, smaller social media platforms trended on Twitter in the hours after the announcement as users debated whether to move elsewhere.

Star Trek actor George Takei also voiced concerns about the takeover but said he planned to stay on the site and encouraged others to do the same.

“I’m not going anywhere. Should this place become more toxic, I pledge to strive even harder to lift up reason, science, compassion and the rule of law,” he said.

“The struggle against fascism, misinformation, and hate requires tough fighters. I hope you stay in the fight, right beside me.”

Following the takeover announcement, Mr Musk described Twitter as “the digital town square” in a joint statement with the social media platform.

“Free speech is the bedrock of a functioning democracy, and Twitter is the digital town square where matters vital to the future of humanity are debated,” he said.

He added that he wants to make Twitter “better than ever”, promising to get rid of spam bots and to open the platform’s algorithms to the public to increase trust.

Responding to the news, Downing Street said that “regardless of ownership, all social media platforms must be responsible”.

“That includes protecting users from harm on their sites,” the Prime Minister’s official spokesman said.

“It is too early to say what – if any – changes will be made to how Twitter operates.

“It remains an important tool, it’s used by world leaders, and we will continue to work with them to make sure it continues to improve.”

It was “entirely a matter for Twitter” whether former US president Donald Trump’s account was reactivated, the spokesman added.