A union representing Google employees is demanding the tech giant lift what it called an illegal “gag order” barring them from discussing landmark antitrust cases that could upend the company’s business.

On Aug. 5, US District Judge Amit Mehta ruled that Google is a “monopolist” with an illegal stranglehold over the online search market.

That same day, Google president of global affairs Kent Walker instructed employees not to comment on the case inside or outside the workplace.

The Alphabet Workers Union alleges that Walker violated a federal labor law with the “overly board directive” in a bid to “suppress worker speech” related to the antitrust battles, according to a copy of the Aug. 15 filing obtained by The Post.

“Our employer continues to demonstrate a blatant disregard for federal labor law and our right to discuss working conditions with coworkers—up to and including the proposed remedies of federal antitrust actions that could affect many of our jobs at Google,” said Parul Koul, a Google software engineer and president of Alphabet Workers Union.

Mehta is expected to decide on remedies to address Google’s search monopoly by next summer.

The Justice Department recently indicated that it could seek a breakup of Google through a forced divestment of parts of its business, such as its Chrome web browser.

Google pushed back on the union’s complaint.

“We respect Googlers’ rights to speak about their terms and conditions of employment,” Google spokesperson Peter Schottenfels said in a statement. “As is standard practice, we’re simply asking that employees not speak about ongoing litigation on behalf of Google without prior approval.”

The Verge was first to report on the complaint.

The labor complaint is the latest sign of discord between Google and its workforce. In April, the tech giant fired dozens of employees who engaged in anti-Israeli sit-ins at offices.

A separate DOJ antitrust case targeting Google’s alleged monopoly over digital advertising technology is also underway. Closing arguments in that case are scheduled to kick off next month.

Google CEO Sundar Pichai has admitted that the company will likely be tied up in court for many years as it fights the cases.

In a lengthy statement, the Alphabet Workers Union said it is “crucial that workers are engaged and our views and interests considered during the decision-making process around antitrust remedies.”

“That has yet to happen,” the union added.

Google has vowed to appeal the judge’s ruling and pushed back on the DOJ’s proposed remedies – calling it a “radical” framework that would go “far beyond the specific legal issues in this case.”