Elon Musk is seeking to dismiss a lawsuit by US regulators alleging he wrongly saved money by revealing he increased his initial investment in Twitter too late.

The US Securities and Exchange Commission (SEC) said in a January complaint that Musk failed to disclose that he had built up his stake in the company within the regulator’s timeframe.

It said this had allowed him to save about $150m (£123m) by purchasing shares in Twitter – which he bought outright months later and renamed X – at “artificially low prices”.

Musk’s lawyers, filing shortly before the court’s deadline for his response, called the lawsuit “a waste of this Court’s time and taxpayer resources”.

“The SEC does not allege that Mr. Musk caused any investor harm. Rather, the SEC alleges that Mr. Musk late-filed a single beneficial ownership form three years ago, and fully corrected any alleged error immediately upon its discovery,” they said in their Thursday filing.

“There is no ongoing violation. There is no intent. There is no harm.”

In its January complaint, the SEC alleged that Musk violated US securities rules requiring investors to disclose within 10 days if their holdings in a company surpass 5%.

It said Musk should have revealed he had crossed the threshold for disclosure of shares by 14 March 2022, but he did not disclose it until 21 days after his purchase – on 4 April.

“Musk’s violation resulted in substantial economic harm to investors,” it claimed.

During a prior investigation by the SEC into Musk’s purchase of Twitter, he gave two depositions – with mystery surrounding whether he appeared at a further interview.

When the SEC filed its lawsuit in January, Musk blasted the regulator as a “totally broken organisation” on social media and accused it of wasting its time.

His lawyers’ formal response, submitted on Thursday, also accused the SEC of targeting the executive in a “relentless pursuit”.

“The Commission’s selective enforcement against Mr. Musk – seeking monetary relief more than 1,500 times larger than the relief imposed on similarly situated individuals in similar cases – reveals an agency targeting an individual for his protected criticism of government overreach,” it said.

It said other investigations launched by the watchdog over the past seven years – including one in which he was eventually cleared by a jury of wrongdoing over a tweet about the future of Tesla’s ownership – reflected “relentless scrutiny”.

The SEC declined to comment.