Independent Democrats leader Patricia de Lille has asked the director of the National Prosecuting Authority to give her his full reasons for not prosecuting Jacob Zuma.

Her lawyers sent the letter to Bulelani Ngcuka yesterday. It stated that De Lille was subjected to severe pressure from parliament when she first made revelations about the arms deal, and that Ngcuka threatened her with prosecution.

Most opposition parties upped the ante on calls earlier in the day on Zuma to resign, and said he should immediately step down if he could not refute the allegations.

De Lille first threatened to take legal action after Ngcuka's statement on Saturday that there was prima facie evidence against Zuma, but that he would not be prosecuted as the case was not "winnable".

Yesterday her lawyers told Ngcuka to confirm these statements by September 1 and provide De Lille with full reasons why the deputy president would not be charged.

On September 19 1999, De Lille first made the startling accusation that members of the government were involved in corruption in the arms deal.

After an initial legal perusal of documents provided by her and parliament's standing committee on public accounts (Scopa), President Thabo Mbeki announced in January 2000 that there was no prima facie evidence against anyone in the government pertaining to the arms deal.

"They claimed there was no prima facie evidence, and now they are admitting there is, but they are still not prosecuting Zuma," De Lille said.

She said Zuma was the person she had referred to when she said that someone "high up in the government" was allegedly involved.

De Lille's lawyers told Ngcuka she had a "direct interest in corruption in the arms deal" and intended taking legal action.

She told Independent Newspapers that, in terms of the latest revelations, "I still maintain my point that the only way he is going to be cleared is by appearing in an open court, where the court will decide whether he is guilty. We are missing an opportunity."

Another person who fell foul of the allegations around the arms deal, former Scopa chairperson Gavin Woods, of the Inkatha Freedom Party, yesterday welcomed the fact that the state "acknowledged the significance of the letter" written to him in person by Zuma on January 19 2001.   

In the charge sheet against Shaik, the letter is cited as possible evidence that Zuma was allegedly honouring an alleged bribe solicited from Thomson-Thales, a beneficiary of the arms deal.

Woods said the letter was copied to foreign companies, such as Thomson, while it accused him (Woods) of insulting foreign arms dealers.

The letter also suggested there was no need for the former Heath unit to be involved in an inquiry and that Zuma hoped the inquiry was not aimed at finding "the executive guilty at all costs".

Woods called on Mbeki to "consider calling together all aggrieved, affected and relevantly knowledgeable parties in order to discuss finding ways of dealing with the outstanding questions, intrigues and controversies which continue to surround the arms deal ... to close the door on this ugly chapter ..."

Democratic Alliance chief whip Douglas Gibson said yesterday the "cloud which hung over Zuma over the weekend has turned into a full-blown tornado".

"How can he possibly carry on as deputy president ... in the face of these allegations?

"Unless he can decisively refute them, and do so immediately, his deputy presidency has suffered a mortal blow.

"He will have to go."

United Democratic Movement leader Bantu Holomisa also asked for Zuma's immediate resignation. "We don't need to prove anything beyond reasonable doubt, because the evidence of probability is enough."

African Christian Democratic Party leader Reverend Kenneth Meshoe said: "Zuma must either prove his innocence or step down."

The New National Party's Carol Johnson, however, said this might be premature. "Let's assume he is innocent until proven guilty, and let a court find him guilty. It is crucial that they push for a prosecution."

With acknowledgements to Christelle Terreblanche and The Star.