Twitter’s lawyers have threatened Meta CEO Mark Zuckerberg with legal action, claiming Meta used “trade secrets” and “highly confidential information” it gathered from disgruntled former Twitter staff to build competing app Threads which launched on Thursday morning.

In the letter, first reported by Semafor, lawyer Alex Spiro claims Meta had “engaged in systemic, willful, and unlawful misappropriation of Twitter’s trade secrets and other intellectual property”.

“Over the past year, Meta has hired dozens of former Twitter employees,” the letter says.

“Twitter knows that these employees previously worked at Twitter, that these employees had and continue to have access to Twitter’s trade secrets and other highly confidential information.”

Spiro goes on to say that Meta took on these staff to spin up its Twitter clone Threads, accelerating the app’s development using “trade secrets and other intellectual property” from the Elon Musk-owned company.

Musk notoriously fired staff who were critical of his approach to running the company he bought for $61 billion (US$44 billion) last year.

In response to reports about sacking employees who stirred disquiet during the transitionary period Musk sarcastically apologised “for firing these geniuses”, adding that “their immense talent will no doubt be of great use elsewhere”.

A regional spokesperson for Meta told Information Age they would not comment for this story, pointing instead to a statement from the company’s communications director Andy Stone that was already published by Semafor.

“No one on the Threads engineering team is a former Twitter employee – that’s just not a thing,” Stone said.

Twitter’s press team replied to Information Age’s request for comment with an automated poo emoji.

Twitter’s lawyers said the company “intends to strictly enforce its intellectual property rights”, demanding the Mark Zuckerberg company “take immediate steps to stop using” any allegedly stolen trade secrets.

Responding to reports about the legal letter, Musk tweeted “competition is fine, cheating is not”.

According to Zuckerberg, Threads – which syncs directly with Instagram – had 30 million sign ups in its first day as users flocked to the app’s chaotic text-based feed which had limited features (no hashtags, direct messages, or a ‘following’ feed) at launch.