President Thabo Mbeki on Tuesday "amended and clarified" the terms of reference for the Hefer Commission of Inquiry.

The commission - probing spying allegations against National Director of Public Prosecutions Bulelani Ngcuka - will resume its public hearings on Wednesday in Bloemfontein.

The office of the presidency said in a statement on Tuesday that the change to the terms of reference was necessitated by the need to clarify the fact that the commission was not required to investigate whether Justice Minister Penuell Maduna was an agent of the apartheid government, and that the alleged abuse of power related only to the office of the national director of public prosecutions.

"It also became necessary to make it clear that the commission was necessitated by allegations made by persons outside the state security services."

The substance of the investigation remained, largely, the same. The changed term of reference now reads:

"The commission must inquire into, make findings and report on the allegations made by Messrs Maharaj and Shaik that the national director of public prosecutions was an agent of the security services of the pre-1994 government under code name RS452 or any other code name and, as a result thereof, improperly and in violation of the law, had taken advantage of or misused the prosecuting authority and, in particular, abused, advanced, promoted, prejudiced or undermined the rights and/or interests of any person or organisation."

The African Christian Democratic Party said on Tuesday that its leader, Reverend Kenneth Meshoe, would address the Cape Town Press Club on Thursday on "the issue of why the government chose to investigate spy allegations rather than corruption allegations".

A number of witnesses from the intelligence and media communities have been subpoenaed to appear before the commission this week.

These include members of intelligence organisations from both the apartheid era and the post-1994 government.

Among the witnesses scheduled to be called on Wednesday are apartheid-era police chief General Johan van der Merwe and National Police Commissioner Jackie Selebi.

Three journalists were summoned to testify on Thursday. They are Elias Maluleke from City Press, former senior Sunday Times political correspondent Ranjeni Munusamy, and e-tv editor-in-chief Joe Thloloe.

From Monday Ngcuka's main accusers, Mac Maharaj and Mo Shaik, will be called to the stand.

Commission secretary John Bacon said on Tuesday no proving documents had been received yet as requested from the summoned.

He also received no notice of any of them refusing to attend the scheduled hearings.

Wednesday's hearings will start at 9am at the Iustitia Building in Bloemfontein. - Sapa