Billionaire Elon Musk is under investigation by the U.S. Securities and Exchange Commission over his 2022 purchase of social media giant Twitter, according to a Thursday court filing in which the agency sought to compel Musk to provide testimony.

The investigation concerns whether Musk broke federal securities laws in connection with his 2022 purchases of stock in Twitter, which Musk renamed X, as well as statements and SEC filings he made in relation to the deal.

The SEC said it subpoenaed Musk in May 2023 requiring him to provide testimony at the SEC’s San Francisco office, and that Musk had agreed to appear last month. But then two days beforehand Musk raised "several spurious objections" and told the SEC he would not appear, the SEC said. Musk also refused to SEC proposals to conduct the deposition in Texas in October or November.

Musk acquired Twitter last year after initially building a large minority stake in the social media platform, which he allegedly failed to disclose in a timely manner.

"The SEC has already taken Mr. Musk's testimony multiple times in this misguided investigation - enough is enough," said a statement from Alex Spiro, an attorney for Musk.

In a statement, the SEC said it was seeking "Musk’s testimony to obtain information not already in the SEC’s possession that is relevant to its legitimate and lawful investigation."

Musk and the SEC have a long-running feud that dates back to Musk's 2018 tweet that he planned to take his electric carmaker Tesla private and had funding secured.