Elon Musk restarted subscription services for Twitter on Monday after the first attempt saw an embarrassing fake ad that scared advertisers and cast doubt on the site's future.

The first trial last month came just 10 days after Musk took over the influential platform for $44 billion and a series of layoffs that devastated the company's workforce, including a union that organizes content.

The resurgence of Twitter Blue comes as the Tesla and SpaceX owner has stepped up his tweets in support of right-wing causes, including opposition to the use of gender pronouns in the US government's response to Covid-19.

The subscription service costs $8 a month for users accessing Twitter on the web and $11 if they sign up on an Apple device. The additional cost can be explained by Musk's anger that Apple is charging up to 30% commission on its App Store.

The first deployment of Twitter Blue caused chaos when several fake accounts appeared claiming to be celebrities or businesses and Musk's team was forced to dismantle the system. This time, the company has used Twitter's review to improve its approval process before getting the blue check mark.

The check mark is now gold for businesses and later in the week will turn gray for government members, the company said. The blue check on the account, which shows that Twitter has checked it, was previously free but only members and the public in an effort to prevent crime and misinformation.

According to the site, the new Twitter Blue subscription is currently available in the United States, Canada, Australia, New Zealand and the United Kingdom, "with plans to expand".

- 'Another lockdown' -

Since taking over, content control has proven to be a headache for Musk, who has described himself as a free speech advocate and vowed to end most forms of censorship on the site.

But the billionaire's commitment to free speech has sparked media attention, caught the attention of regulators and briefly challenged the company's access to Apple's App Store.

Musk believes the former Twitter owner has a hard-left and pro-LGBTQ stance and wrongly banned accounts, including that of former President Donald Trump.

On Sunday, he fired the top adviser on the US response to the Covid-19 pandemic, Anthony Fauci, who was a frequent target of vitriol in the right-wing media.

"My pronouns are Prosecute/Fauci," Musk said, tauntingly playing on the growing practice for people to indicate their preferred gender pronouns.

Musk also posted a meme showing Fauci telling US President Joe Biden, "Just one more lockdown, my king..."

Early in the pandemic, Musk tweeted that concern over the virus was "dumb" and since taking over Twitter has removed its policy targeting Covid misinformation.

The White House blasted Musk for the tweets against Fauci calling them "disgusting" and "divorced from reality".

"These are incredibly dangerous, these personal attacks that we are seeing," said White House spokeswoman Karine Jean-Pierre.

CNN reported that Twitter's former head of trust and safety had fled his home after baseless attacks on Twitter, endorsed by Musk.

Yoel Roth, who left the company in November, has been the subject of threats following the release of the Twitter Files, a trove of internal documents that Musk alleges demonstrates collusion within the company with the Democratic Party.

The attacks took a serious turn Sunday when Musk endorsed a tweet that accused Roth of being an apologist for pedophilia — a common trope used by conspiracy theorists to target opponents.

The South African-born billionaire's embrace of right-wing talking points seemed to attract increasing scorn in politically liberal San Francisco, where Twitter is headquartered.

Musk was loudly booed by a crowd in the city late Sunday after he was invited on stage by comedian Dave Chappelle.

"It's almost as if I've offended San Francisco's unhinged leftists... but nahhh," Musk tweeted after the event.

Carolina Milanesi, a tech analyst for Creative Strategies, warned that Musk's political turn on Twitter could be problematic for the company going forward.

With engagement down significantly, the return on investment for promoting tweets has "crashed," she said.