The bill, which still has to clear the lower house, sailed through by 34 votes to 16 despite opposition attempts to persuade lawmakers to reject it.

The government says the bill will replace outdated apartheid laws on classified information and espionage.

But it has met fierce opposition in a country where the media regularly exposes government wrongdoing and excess.

One recent story gave details of a $28 million upgrade to President Jacob Zuma’s private home, thanks to internal documents that had been leaked to the press.

The bill carries heavy penalties, including jail terms of up to 25 years, and activists have slammed it as a threat to democracy.

It will now be sent back to the main chamber, the National Assembly, for approval in 2013 after undergoing 800 changes in the past 11 months. This chamber approved an earlier version of the bill last year.

“To those who fear that the bill may be abused, we say: the only thing to fear is fear itself,” State Security Minister Siyabonga Cwele told lawmakers ahead of the vote in the upper chamber, the National Council of Provinces.

The bill aimed to criminalise espionage and information peddling, not to cover up corruption, “limit scrutiny or prevent embarrassment,” the minister argued.

“Let me assure you again that this bill does not permit the abuse of power,” he added.

The draft law has been one of post-apartheid South Africa’s most controversial pieces of legislation.

It has provoked alarm from democracy icons including Desmond Tutu. Nelson Mandela’s office has also expressed concern, as has the ANC’s key labour federation ally the Congress of South African Trade Unions (COSATU).

Watchdogs, while welcoming the new amendments, have warned that the redrafted version still carries the threat of “draconian” jail terms of up to 25 years if a case is deemed to be espionage related.

Simply holding or disclosing classified data is punishable by a maximum of five years imprisonment.

The main opposition Democratic Alliance (DA) tried to postpone the debate and the vote, arguing that the amended version had not been distributed before the house gathered. But that bid failed.

“Given the extremely high levels of corruption that we see in government today, it is inevitable that the bill enacted will be used to cover up crime and corruption by those who wish to escape exposure,” said DA lawmaker Alf Lees.

Lobby group the Right2Know campaign has argued that the bill could have people locked up for having or passing on information such as that released by Wikileaks.

“It penalises everyone down the chain of disclosure,” spokesman Murray Hunter told AFP. He argues that there was no full public interest defence to justify whistleblowers who leaked information that should have been in the public domain.

Hard-won gains however did include a partial public interest defence on the lesser offences.