The evidence of Mo Shaik that he kept a secret database of intelligence agents and that only Jacob Zuma, the deputy president, can corroborate his claims that Bulelani Ngcuka, the national director of prosecutions, was a spy, has created a dilemma both for Zuma and the African National Congress.

Shaik also implicated Zuma directly this week by telling the Hefer commission that the deputy president had advised him not to hand over any information to Penuell Maduna, the justice minister, who had asked Shaik in 2001 whether Ngcuka had been investigated as a suspected apartheid spy.

Shaik's evidence, which failed to substantiate the crumbling spy claims, seems to have set him on a collision course with Zuma - the man whose flag he said he wanted to fly - and the ANC, for whom he worked as a top intelligence official during the apartheid era.

Shaik's startling evidence about his encoded database casts doubt over the statement made by the ANC to the commission in October that all "ANC records with respect to matters of intelligence were handed over to the relevant state institutions during the period of transition".

Either the ANC did not know about Shaik's files, to which Zuma apparently has access, or it did know but did not regard them as ANC files, or it made a false statement.

Shaik told the commission that he was never requested by either the ANC or the intelligence services to hand over his databases. This was despite the fact that he became a high-ranking National Intelligence Agency (NIA) official in 1994.

It begs the question as to whether the ANC was aware of Shaik's collection of about 888 secret files on suspected informers, and whether it decided to turn a blind eye to it during the transition.

Smuts Ngonyama, the head of the presidency in the ANC, in whose name the original statement to the commission was made, said on Saturday that the statement reflected the ANC's formal position and there was not likely to be any change until the Hefer commission was concluded.

"But we do acknowledge the contradiction between the ANC statement and Shaik's evidence," he said. Ngonyama said the ANC position remained that it was not necessary for Zuma to testify before the commission.

But the commission is likely to come under renewed pressure to call Zuma after Shaik's claim that Zuma held the key to the spy allegations and had instructed Shaik not to tell Maduna about the spy claims.

Zuma's office dodged the implications of Shaik's claim. "As is a matter relating to ANC intelligence matters, we wouldn't want to encroach on their territory," said Lakela Kaunda, Zuma's spokesperson.

In a separate interview at the ANC list conference yesterday, Kgalema Mothlanthe, the ANC secretary-general, denied the ANC had contradicted itself and he stood by the October statement that all ANC files had been handed over.

"There is no contradiction. We don't know about that (Shaik's data-base). Those are not ANC files," he said. Mothlanthe said that he understood Shaik had himself told the commission that the ANC did not know about the files.

Asked whether the ANC was rethinking whether Zuma should testify before the commission, Mothlanthe said: "He never headed a Zuma family intelligence. He headed an ANC intelligence unit and all of that was integrated at the time of liberation and now is located in the NIA. So there is no basis for him to go and testify about that."

Shaik asked Judge Joos Hefer to find another independent source, rather than allowing lawyers to destroy his evidence. He suggested the commission should call Zuma to back up his testimony.

Zuma may be the only person able to confirm that the ANC did in fact investigate Ngcuka in the late 1980s, and did not concoct the evidence more recently, in the wake of corruption investigations into Shaik's brother, Zuma and Maharaj.

What raised the most eyebrows this week, however, was the confession by Shaik that as head of the ANC underground's Mandla Judson Kuzwayo (MJK) intelligence unit in the 1980s he built up two data banks with information on 888 suspected informers and that he still possesses and maintains it.

John Bacon, the commission secretary, indicated that there would have to be a reassessment of wit-nesses after Shaik's cross-examination and a second attempt to get evidence from journalists. The commission would then also be able to send a first interim report to President Thabo Mbeki.

With acknowledgements to Christelle Terreblanche, John Battersby, Jeremy Michaels and the Sunday Independent.