Former national director of public prosecutions Bulelani Ngcuka on Sunday lashed out at suggestions that his conduct was to blame for the dropping of corruption charges against Jacob Zuma.

"To be direct: the allegation that any conduct on the part of...former Scorpions head [Leonard] McCarthy and I caused, or compelled Mr Mpshe to stop the prosecution of Mr Zuma and Thint is demonstrably false," said Ngcuka in a statement.

Ngcuka issued the statement – the first public comment he has made on the matter since 2009 – in the wake of the public release of the so-called spy tapes.

In 2009, acting National Director of Public Prosecutions, Mokotedi Mpshe cited the tapes in his decision to drop corruption charges against Zuma; saying that they indicated that there was a political conspiracy against Zuma and so the case against him – apparently linked to the arms deal – could not continue.

The charges were dropped shortly before Zuma was sworn in as president of the country.

This week, transcripts of the tapes – in which Ngcuka is heard in conversation with McCarthy – were released following a court order obtained by the Sunday Times.

In one extract, McCarthy tells Ngcuka that: "Ja you know, Zuma will say we are conspiring against him."

Ngcuka said he was speaking out "with some reluctance" but understood that there was "interest and expectation for me to 'say something or be damned'".

Ngcuka said that the way the content of the tapes, "in some instances" had been interpreted; "perpetuates the lie that either myself or Mr McCarthy were in one way or the other to blame...

"It is disingenuous in the extreme to blame me or Mr McCarthy, as Mr Mpshe and the NPA sought to do, for the fact that the prosecution of the accused in this matter was terminated."

Ngcuka said it was not reasonable to connect the discussions he held about the timing of the prosecution to the decision to drop the charges.

He deemed the reported release by the National Intelligence Agency of "secret and raw intelligence" to Zuma's defence team as "a crime".

Earlier on Sunday, Ngcuka also issued a statement to the Sunday Times newspaper about the same matter.