Tesla chief Elon Musk has launched a hostile takeover bid for Twitter, insisting it was a "best and final offer" and that he was the only person capable of unlocking the full potential of the platform.

Musk offered $54.20 a share, which values the social media firm at $43.4 billion, in a filing dated Wednesday April 13 with the Securities and Exchange Commission.

Twitter's board said it would carefully review what it termed Musk's "unsolicited, non-binding" offer and decide on a course of action that was "in the best interest of the Company and all Twitter stockholders."

Musk's latest move toward Twitter comes just days after he turned down a seat on the board following his acquisition of a 9.2 percent stake in the microblogging platform.

"I invested in Twitter as I believe in its potential to be the platform for free speech around the globe, and I believe free speech is a societal imperative for a functioning democracy," Musk said in his filing.

"However, since making my investment I now realize the company will neither thrive nor serve this societal imperative in its current form," he said.

"Twitter needs to be transformed as a private company. As a result, I am offering to buy 100% of Twitter for $54.20 per share in cash, a 54% premium over the day before I began investing in Twitter."

Popcorn time

Musk, Twitter's biggest shareholder, said his "offer is my best and final offer" and he would reconsider his position as a shareholder if it was rejected.

"Twitter has extraordinary potential. I will unlock it," he said.

Wedbush analysts said the Twitter board would likely be forced to accept the bid or seek another buyer. 

"It's get out the popcorn time as we expect many twists and turns in the weeks ahead as Twitter and Musk walk down this marriage path," the analysis said, with a host of questions likely to swirl around issues of financing, regulatory aspects and balancing Musk's time between his many companies.

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. His announcement sent Twitter shares soaring more than 25 percent.

He was offered a seat on the board but turned it down at the weekend.

Musk's move comes 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 -- which includes himself at number eight, with 81 million followers.

In other weekend tweets, Musk posted joke polls on whether to drop the "w" from Twitter's name and on converting its San Francisco headquarters to a homeless shelter "since no one shows up anyway."

He also suggested removing ads, Twitter's main source of revenue.

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.