Twitter's largest shareholder Elon Musk has offered to buy 100% of Twitter Inc. as the world's richest man looks to transform the microblogging platform as a private company.

"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 and a 38% premium over the day before my investment was publicly announced," Musk wrote in a letter to Bret Taylor, chairman of the board at Twitter.

"My offer is my best and final offer and if it is not accepted, I would need to reconsider my position as a shareholder," the Tesla founder said. The offer values Twitter at $43 billion.

Elon Musk said he invested in Twitter as he believes in its potential to be the platform for free speech around the globe. "I believe free speech is a societal imperative for a functioning democracy. However, since making my investment I now realize the company will neither thrive nor serve this societal imperative in its current form," Musk wrote in the letter. "Twitter needs to be transformed as a private company."

Musk stated that Twitter has extraordinary potential that he will unlock. "I believe that the company should be private to go through the changes that need to be made. After the past several days of thinking this over, I have decided I want to acquire the company and take it private," he said.

"I am not playing the back-and-forth game. I have moved straight to the end," Musk said. "If the deal doesn't work, given that I don't have confidence in management nor do I believe I can drive the necessary change in the public market, I would need to reconsider my position as a shareholder. This is not a threat, it's simply not a good investment without the changes that need to be made. And those changes won't happen without taking the company private," he added.

Twitter later confirmed that it has received an unsolicited, non-binding proposal from Musk to acquire all of the company's outstanding common stock for $54.20 per share in cash.

"The Twitter board of directors will carefully review the proposal to determine the course of action that it believes is in the best interest of the company and all Twitter stockholders," it stated.

This comes days after Twitter chief executive officer Parag Agrawal said Elon Musk will not be joining the company's board.

The Tesla CEO had acquired a 9.2% stake in Twitter by purchasing nearly 73.5 million shares. Musk's shareholding is more than four times the 2.25% stake held by Twitter founder Jack Dorsey.

"Elon Musk has decided not to join our board... The board and I had many discussions about Elon joining the board, and with Elon directly. We were excited to collaborate and clear about the risks. We also believed that having as a fiduciary of the company where he, like all board members, has to act in the best interest of the company and all our shareholders, was the best path forward. The board offered him a seat," Agrawal said in a note to the company.

Agrawal cautioned that there will be distractions ahead, but the company's goals and priorities remain unchanged. "The decision we make and how we execute is in our hands, no one else's. Let's tune out the noise, and stay focused on the work and what we're building."

Elon Musk to buy Twitter

'Not playing the...game': Elon Musk makes $43 bn hostile takeover bid for Twitter