South Africa's anti-apartheid leader Desmond Tutu is urging the country's parliament to reject a controversial bill that would make it illegal to divulge state secrets.

The bill would punish those who publish classified information with up to 25 years in jail.

Tutu says the law is “insulting” to South Africans, and that it would effectively outlaw whistle-blowing and investigative journalism.

The bill is expected to pass parliament on Tuesday with the support of the ruling African National Congress party.

The new law would outlaw the release of classified documents, even if the information contained details that could benefit the public.

Critics of the bill held protests Tuesday at ANC headquarters, wearing black to show their opposition – a reference to a 1970s apartheid-era press crackdown.