ON Tuesday morning, my friend Stefaans Brummer, arguably South Africa's best investigative journalist, sent me a text message. “When I'm incarcerated at Parkview police station, please bring me coffee, a muffin and a hacksaw blade,” he wrote. I don't do coffee or muffins, I replied jokingly, but I might deliver the hacksaw.

Brummer and his colleagues were threatened with 15 years in jail. In response, they blacked out the front page of the paper and the story. This proud anti-apartheid paper looked last Friday exactly as it would have in 1989, at the height of apartheid censorship and harassment of journalists.

It is not the first time that journalists have been harassed and threatened with jail. Last year an investigative journalist who exposed multimillion-dollar police corruption was arrested, driven through the night to a remote location and questioned at 2am.

Over and above the petty harassment, the ANC has vigorously pursued attempts to set up a government-led tribunal to regulate the print media. Since the ascent of Zuma and his coterie of securocrats to power in 2009, we journalists have been living with our hearts in our mouths, afraid that the party of Mandela would veer away from the open society it had fought for and join the likes of Zimbabwe and Equatorial Guinea — countries whose secrecy laws allow them to jail journalists at will.

For years we had pointed to the north, saying such draconian laws would never arrive here. Not in the land of the ANC, Africa's oldest liberation movement, steeped in the values of openness and dedicated to the fight against corruption.

The new South Africa is not comparable to the evils of old. But on Tuesday, when parliament passed a state secrecy law, we were shamed. The ANC became like its apartheid predecessors. The party of Mandela ignored the man himself and muzzled whistleblowers, journalists and its own citizens. It defied its trade union allies and civil society, and used its majority to ram through the protection of information bill, which gives the state power to classify information and criminalise anyone who comes into possession of such classified information. Brummer and their sources face up to 25 years' imprisonment.

The bill also seals off state security agencies from any kind of scrutiny or accountability to the public — meaning that any investigation that, for example, mirrors the work done by American journalists to expose Richard Nixon and the Watergate scandal would be criminal. Crucially, the bill has no public interest defence.

After the legislation was passed, members of the South Africa National Editors' Forum — all dressed in black — left parliament. ANC MPs jeered and shouted: “Bye, bye.” Power and incumbency have not been easy for the ANC. The party, which turns 100 in January 2012, is riven with divisions. Corruption allegations surface every day, with the World Economic Forum pointing out that corruption is among the top four concerns of potential foreign investors.

This has led to paranoia and fear in the party. State security agencies are used to target political opponents, with the latest scandal leading to the head of domestic intelligence being fired for spying “for the wrong side” (opponents of Zuma) two months ago. The party of freedom has turned into the party of fear. In such a climate, the media and civil society have become the enemy.

But for those of us who have watched the passage of this bill with a growing horror, the battle is not over. The bill goes before the second house of parliament and, if passed, to the president for signature. We are hoping that Zuma will throw it back. Should he sign it into law then a constitutional challenge awaits.

For now, though, we feel betrayed by a party that once made media freedom one of its pillars. The ANC, riven by internal battles, is beginning to take the country down with it. It has lost its way. It has blinded itself. For us, it is time for a new, long and hard struggle.

The writer was founding editor of This Day newspaper in South Africa. — The Guardian, London