Southern Africa's Catholic bishops have expressed regret about the passing of a parliamentary bill that expands protection for State secrets and has asked the national president to refer the bill to the country's constitutional court.

"We regret that the Protection of State Information Bill was passed by the National Assembly yesterday (April 25)," the bishops said in a statement signed by Cape Town Archbishop Stephen Brislin, president of the Southern African Catholic Bishops' Conference.

"While improvements have been made to the bill there are still flaws which are a cause for concern," the bishops said in a statement on April 26.

The bishops regretted that South Africa's parliament passed the bill expanding protection for State secrets, noting that the country needs more transparency, not more secrecy, to fight corruption.

They urged President Jacob Zuma, who must sign the proposed law, known as the "Secrecy bill" before it becomes law, to refer it to the Constitutional Court for deliberation in order to protect the democracy "we all cherish."

The bill has also been criticised by the main opposition party, the Democratic Alliance.

When it was first drawn up it was strongly criticised by civil society groups, academics, trade unions, journalists, writers including Nobel Literature laureate Nadine Gordimer and Nobel Peace Prize laureate archbishop emeritus Desmond Tutu.

Citics said the bill was originally worse than the apartheid era law it was replacing.

Mamphela Ramphele, a co-founder of the black consciousness movement and leader of the new Agang party, said: "I would like to see that bill tested and measured against the standards in our constitution."

She said the law should allowed unobstructed access of all citizens to information and there should be no punishment of people who reveal misdeeds.

"As we have seen, whistleblowers have been hammered and so people have stopped blowing the whistle," said Ramphele. "Without that sense of being protected by the law, protected by the constitution, people are going to be even more afraid and this bill is a very bad sign."

The bill "lacks a full public interest defense and will thus make the fight against corruption more difficult," the bishops said in their April 26 statement

"The penalty clauses provide that severe punishment (up to 25 years in prison) can be imposed if someone discloses a secret that the person 'knows or ought reasonably to have known' would benefit a foreign state. This, in effect, creates an excessive penalty for a possible negligence crime," the bishops said.