A committee of South African politicians has approved draft legislation which aims to safeguard state secrets, a measure civil rights activists and opposition parties say may violate the constitution.
The ruling African National Congress used its majority on the panel to adopt the Protection of State Information Bill, which proposes jail sentences of as long as 25 years for anyone accessing classified information.
Politicians representing three opposition parties voted against the bill at a hearing in Cape Town yesterday.
The bill will now be voted on in Parliament, before being referred to President Jacob Zuma to sign into law.
"I don't think one can expect any more radical changes to the bill during the parliamentary process," said Murray Hunter, convener of the Right2Know campaign, which opposed the bill on the grounds that it would violate rights to free speech and hobble efforts to expose corruption.
"It's deeply problematic."
In June, the ANC buckled to pressure to limit the scope of the law to protect information that had the potential to undermine national security, rather than the broader national interest.
It rejected calls for the insertion of a clause allowing such information to be released in the public interest.
The Freedom Front Plus, an opposition party, said it would ask the Constitutional Court, the country's highest judicial body, to determine whether the omission of a public interest defence was lawful.
"We believe that the exclusion of the defence gives too much power to the Government to classify information as confidential and will therefore not withstand the test of constitutionality," the party said in an emailed statement.
The bill proposes that anyone who releases or receives top secret information for the purposes of espionage be jailed for between 15 years-25 years.
It envisions sentences of between three-15 years for lesser offences relating to the access and possession of classified documents.
"The penalties are incredibly harsh" and will serve as a deterrent to whistle-blowers, Right2Know's Hunter said in an interview in Cape Town.
Right2Know represents more than 400 organisations and 16,000 individuals.
Its backers include cleric Desmond Tutu and author Nadine Gordimer, both of whom are Nobel laureates.