Activists and media organisations in the Philippines have denounced Rodrigo Duterte’s government after its lawyers moved to strip the nation’s biggest media group of its franchise in the most severe attack on press freedom in the country yet.

Duterte has repeatedly pledged to stop the broadcast operations of ABS-CBN and expressed anger over its reporting during the 2016 presidential election campaign.

A petition filed with the country’s top court alleges that ABS-CBN violated a restriction imposed by the constitution on foreign ownership of mass media by allowing overseas investors to join the company.

“We want to put an end to what we discovered to be highly abusive practices by ABS-CBN,” the solicitor general, Jose Calida, said in a statement. “A franchise is a special privilege granted by the state, and should be restricted only to entities which faithfully adhere to our constitution and laws.”

Other media outlets closed ranks and rallied in support of ABS-CBN on Monday. “We stand with our colleagues at ABS-CBN and share the hope that they will weather this and come out even stronger,” the news website Rappler said in a statement. “The Duterte administration, through Calida, is resorting to legal gymnastics to push their own agenda of silencing critical media.”

The network’s franchise expires on 30 March. Early in his term Duterte had accused it of failing to broadcast his campaign advertisements and not returning the payments. The president has repeatedly vowed in public speeches to block any new licence, and a proposed law that would give ABS-CBN a 25-year operating permit has been gathering dust in congress since mid-2016.

Duterte taunted the network in a speech in December, telling its owners to sell it. “ABS-CBN, your contract is about to expire. If I were you, you’re better off selling it,” he said. “I will make sure that you will remember this episode of our times forever.”

The government used the same accusation about foreign ownership against Rappler, which in 2018 had its licence revoked in a decision that is under appeal. The website, along with its editor, Maria Ressa, faced a string of legal charges related to its critical reporting.

The National Union of Journalists of the Philippines (NUJP) led a protest rally on Monday afternoon. Protesters gathered near the headquarters of ABS-CBN carrying megaphones and placards bearing slogans such as “defend press freedom”. On social media, many journalists also shared the logo of ABS-CBN to declare their support.

“This government is hellbent on using all its powers to shut down the broadcast network,” the NUJP said in a statement. “This is not just about ABS-CBN. This is not just about the Philippine media. This is about whether anyone can or should deprive you, the Filipino people, of your right to know.”

Nonoy Espina, the NUJP chairman, said that should the government succeed with the petition, it would open doors for similar cases against the media in the future. “If they shut ABS-CBN down, then that’s one big voice lost and it will make it easier for them to start shutting down the other voices that they do not agree with,” he said.

The National Union of People’s Lawyers (NUPL) said Duterte’s latest move was reminiscent of the martial law years under Ferdinand Marcos. “During those years, the media was put under government control and the information flow was restricted,” said the NUPL secretary general, Ephraim Cortez. “Independent journalists and media workers were similarly threatened and silenced with false charges.”

The Foreign Correspondents Association of the Philippines said: “These moves politically harass and threaten a pillar of the media industry that employs thousands of Filipinos and has played a crucial part in helping fight official corruption and abuse for decades.

“Our ABS-CBN colleagues have been on the frontlines of every major breaking news in the country … We call on our supreme court justices to side with the people’s right to truthful and independent news, the constitution and democracy.”

Agence France-Presse contributed to this report