Elon Musk no longer joining Twitter board: CEO, Brendan Smialowski / AFP

Musk was named to join the Twitter board after buying a major stake in the firm and becoming its largest shareholder.

"Elon has decided not to join our board," Twitter CEO Parag Agrawal tweeted.

"Elon's appointment to the board was to become officially effective 4/9, but Elon shared that same morning he will no longer be joining the board," Agrawal said.

"I believe this is for the best."

Currently the world's richest man and with more than 80 million followers on the microblogging platform, Musk last week disclosed a purchase of 73.5 million shares -- or 9.2 percent -- of Twitter's common stock.

Agrawal had announced on Tuesday that Musk would be joining the board, describing him as "a passionate believer and intense critic of the service which is exactly what we need".

Musk himself tweeted that he was "Looking forward to working with Parag & Twitter board to make significant improvements to Twitter in coming months!"

In his announcement Sunday, Agrawal shared a note he sent to Twitter, which said Musk's appointment to the board would be contingent on a background check and that he would have to act in the best interests of the company once appointed.

"Elon is our biggest shareholder and we will remain open to his input," Agrawal added.

- Polarizing figure -

In an apparent reaction to the news, Musk tweeted a smirking emoji, without any other comment.

The billionaire tech entrepreneur is a frequent Twitter user, regularly mixing in inflammatory and controversial statements about issues or other public figures with remarks that are whimsical or business-focused.

He has also sparred repeatedly with federal securities regulators, who cracked down on his social media use after a purported effort to take Tesla private in 2018 fell apart.

Musk's decision not to take a seat on the Twitter board came after he tweeted Saturday asking whether the social media network was "dying" and to call out users such as singer Justin Bieber, who are highly followed but rarely post.

"Most of these 'top' accounts tweet rarely and post very little content," the Tesla boss wrote, captioning a list of the 10 profiles with the most followers -- a list which includes himself at number eight, with 81 million followers.

"Is Twitter dying?" he asked.

An outspoken and polarizing figure, the announcement of his appointment to the board had sparked misgiving among some Twitter employees, according to a Washington Post report.

Workers at the California-based social media company cited worries about Musk's statements on transgender issues and his reputation as a difficult and driven leader, according to statements on Slack reviewed by the Post.

A California agency has sued Tesla, alleging discrimination and harassment against Black workers. The electric carmaker has rejected the charges, saying it opposes discrimination.