The Democratic Alliance claims the ANC in the City of Johannesburg wants to develop a secrecy Bill for the municipality.
"Last night [Thursday], the ANC in the City of Johannesburg proposed that the city develop its own secrecy rules," spokesperson Mmusi Maimane said.
He said ANC councillor Sol Cowan proposed the drafting of rules which would allow the city to classify certain documents as "sensitive", making them unavailable for public disclosure.
The DA and all other opposition parties on the city council were opposed to the proposal, Maimane said.
The ANC refused to debate the matter, and the opposition staged a walkout.
"The only motivation for implementing such rules is to cover up corruption and maladministration," Maimane said.
The ANC wanted the secrecy rules after the DA questioned the legality of contracts the city entered into for the hosting of the Miss World competition in 2008 and 2009, he said.
Maimane said over R120-million was spent on the two events.
The contracts were placed before the municipal public accounts committee (MPAC) after the DA had demanded to see them for two years, but on condition that MPAC members sign a confidentiality agreement.
The DA refused to sign the confidentiality agreement, and when the contracts came before council on Thursday night, a rule was attached which would allow for the classification of any document seen as sensitive.
Maimane said: "This is essentially a blank cheque to cover up corruption and maladministration."
Cowan said in a statement on Friday the DA's walkout had generated much hype, but they had very little background on the issues they were displeased about.
"The nub of the disagreement by the Democratic Alliance centres on the Miss World Pageant. As the newly elected chair of [MPAC] it is one of the first issues I have had to deal with."
The investigation had been running for two years, and members of all parties on the committee were given an opportunity to study the contract, on condition its contents remained confidential.
Cowan said it was highlighted that any leak would prejudice the city and leave it open to legal action.
"It must be emphasised that after having studied this confidential contract the MPAC ... could not find any evidence of corruption. The auditor general has come to the same conclusion."
If the DA had evidence to support its allegations, the committee would investigate, Cowan said.
"To date we are still awaiting the lodging of this evidence by the DA."
Cowan said when the report was tabled at the meeting, he recommended the city develop a policy which would allow councillors to view confidential contracts so executive oversight could be effective.
"The DA, in their wisdom, rejected this proposal and walked out of the council. Fortunately council supported the recommendation, and the city will begin to develop a policy on confidential clauses in contracts." - Sapa