The U.S. Securities and Exchange Commission filed a lawsuit against Elon Musk on Tuesday, alleging securities violations in his acquisition of Twitter, now known as X.

According to a complaint filed in federal court in Washington, D.C., the SEC said Musk violated federal securities laws by failing to promptly disclose his 5% stake in Twitter. The Securities and Exchange Commission said Musk waited to disclose the acquisition to build a larger presence in Twitter at a discount.

The lawsuit comes during Gary Gensler's final week as SEC chairman before he steps down on Jan. 20. Gensler and Musk have had several spats over the past four years, including last month when Musk mocked a settlement offer from the SEC office. However, Musk may face a friendlier SEC commissioner when Trump's nominee takes office in a few weeks.

The SEC complaint alleges that Musk disclosed his acquisition of Twitter 11 years late. Musk allegedly purchased more than 5% of Twitter shares on March 24, 2022, after which he was required by the SEC to file a beneficial ownership report. According to the SEC complaint, he filed the report on April 4, 2022.

During this delay in disclosure, Musk allegedly increased his stake in Twitter from 5% to 9%. On the day Musk disclosed the acquisition to the SEC, Twitter's stock price rose 27% from the closing price of the previous trading day. The SEC claimed that this resulted in Musk underpaying more than $150 million for Twitter shares.

In its complaint, the SEC recommended that Musk return unfairly obtained profits and pay additional civil penalties. Ultimately, a federal court will decide whether the SEC's charges are true and whether Musk should be fined.

In a statement to Bloomberg on Tuesday, Musk's attorney Alex Spiro called the complaint an "acknowledgment" that the SEC was unable to bring an "actual case."

"As the SEC retreats and departs, the SEC's multi-year harassment campaign against Mr. Musk culminated in the filing of a single count charge against Mr. Musk," Spiro told Bloomberg.

In a December post on The letter rejected the SEC's settlement offer in the case.

To fill Gensler's position, President-elect Donald Trump nominated Paul Atkins, who served as SEC commissioner during the Bush administration and is expected to be more friendly to Trump's allies. Musk is about as close to Trump as he gets these days, and X's owners could be facing a different regulatory regime in just a few weeks.