Various human rights groups and media houses will be protesting the controversial Protection of State Information Bill (POIB) when it appears before the National Assembly for a vote on Tuesday.

National Press Club (NPC) chairman, Yusuf Abramjee, said the day "will mark the start of a dark day for freedom of speech, freedom of expression and media freedom.

"We have received thousands of messages of support from across SA and it's time that we get a loud and clear message to government that we will not sit back and watch our Constitutional rights being infringed," he said.

"Some political parties, scores of NGO's [non governmental organisations], the Right2Know campaign and Sanef [SA National Editors Forum] have come out in support of 'Black Tuesday."

The NPC asked people opposed to the bill to wear black clothes, a black ribbon or a black armband.

It named the campaign "Black Tuesday", based on what became known as "Black Wednesday" -- October 19 1977, when the apartheid government banned The World, the Sunday World and a Christian publication Pro Veritas, as well almost 20 people and organisations associated with the black consciousness movement.

The ANC'S parliamentary caucus has dismissed the "Black Tuesday" protest as a "distortion of facts".

"The only result this unfortunate comparison and the planned campaign, in which people are urged to dress in black will achieve is to dilute the real history of the Black Wednesday and insult the victims of apartheid's barbaric laws," ANC Chief Whip Mathole Motshekga said on Monday.

Abramjee said the NPC had taken note of the ANC's concerns.

"They feeling the heat and they are trying to side step the issues by attacking the press club," he said.

"They are also trying to defend the POIB...you cannot defend the indefensible."

The NPC has called on government to suspend the scheduled vote.

If the bill is passed, the media will not be able to claim it acted in the pubic interest if it violates or is party to the violation of a law, or publishes classified information to substantiate a report on, for example, malpractice or corruption in government.

On Monday the State Security Agency (SSA) said claims that the bill would lead to censorship and information blackouts were sensationalist.

"It is not correct that there will be mass classification of information as the application of the bill is narrowed drastically to national security departments," SSA spokesman Brian Dube said in a statement.

"To argue that life under the Protection of State Information Bill will be characterised by censorship and information blackouts is sensationalising of the highest order."

The Right2Know Campaign was organising six pickets around the country, including one at Parliament, to protest against the bill.

On Monday the Lesbian and Gay Equality Project (LGEP) said it would urge all lesbian, gay, bisexual, transgendered and intersex (LGBTI) organisations to join the Right2Know Campaign.

"It will be unfortunate that the media is silenced because it is through the media that large volume of information is disseminated and citizens get to know what is happening around them," LGEP director Virginia Setshedi said in a statement.

"This government's move will definitely impact on each and every citizen of the country regardless of what sector or community one belongs to."

On Monday Archbishop Emeritus Desmond Tutu said the bill was flawed and insulting.

"It is insulting to all South Africans to be asked to stomach legislation that could be used to outlaw whistle-blowing and investigative journalism... and that makes the state answerable only to the state," he said in a statement.

Tutu said he was appealing to MPs to acknowledge the backlash the bill had caused.

"Please hear the warnings of the academics, civil society leaders, labour representatives, media corps, and legal and Constitutional experts," he said.

"This law will do our people and our country a disservice."