Controversial entrepreneur Elon Musk has made an offer to buy all of Twitter’s shares.

The “best and final offer” of $54.20 is for 100% of the company, which Musk plans to privatise and transform.

As a 9,2% shareholder – which he disclosed earlier this month – Musk was entitled to a seat on the board, which he rejected this week. It as now emerged, in a filing with the US Securities and Exchange Commission today, that he wants to buy the whole organisation.

“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,” he wrote in his filing.

“However, since making my investment I now realise the company will neither thrive nor serve this societal imperative in its current form. 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 and a 38% premium over the day before my investment was publicly announced.

“My offer is my best and final offer and if it is not accepted, I would need to reconsider my position as a shareholder.

“Twitter has extraordinary potential. I will unlock it.”