The controversial spy tapes that got President Jacob Zuma off the hook on corruption charges were declared illegal during a labour dispute at the CCMA, according to a newspaper report on Wednesday.

The dispute is between the head of the Special Investigations Unit (SIU) Willie Hofmeyr and his former deputy, Faiek Davids, The Times reported.

Ruling in Davids' unfair dismissal application, Bart Ford, a senior commissioner at the Commission for Conciliation, Mediation and Arbitration, found that the recordings were illegally obtained and could not be used in the arbitration hearing.

"It is immediately apparent that the applicant's privacy has been botched... The recordings and evidence in this case was obtained illegally," said Ford.

Ford's ruling is related only to Davids' challenge.

Acting National Prosecuting Authority head Mokotedi Mpshe decided to drop all corruption and fraud charges against Zuma in April 2009. The decision cleared a way for him to become South Africa's president.

Mpshe had found that the secret connivance between Scorpions boss Leonard McCarthy and former NPA head Bulelani Ngcuka in relation to the Zuma case amounted to "intolerable abuse", and that the charges had been influenced by the political infighting of the time.

NPA spokesperson Mthunzi Mhaga told the newspaper it was too early to comment on whether the previous decision not to prosecute Zuma would be affected by Ford's ruling.

"We may have to read the whole judgment/finding and see how that impacts on the NPA," said Mhaga.