Johannesburg - The African National Congress urged government on Thursday to investigate Judge Willem Heath, head of the Special Investigation Unit.

The call followed a letter that the party intercepted which was written by Pan Africanist Congress MP Patricia de Lille and addressed to Heath.

ANC spokesperson Nomfanelo Kota said the relationship between Heath and De Lille was "strange", particularly for a judge who was supposed to be impartial.

In the letter De Lille urged Heath not to hand over evidence relating to the controversial R43 billion arms probe to President Thabo Mbeki.

"The funny thing is how can De Lille correspond with Heath on information like that," she said.

Mbeki has requested information relating to the arms deal and has asked the Heath unit to provide him with all the relevant data it has in its possession.

However, in terms of the law the unit first needs permission from those who gave it the information, Heath unit spokesperson Naomi Goodley said.

Justice Minister Penuell Maduna has also indicated that if the information is not forthcoming, Judge Heath is not above Section 205 of the Criminal Procedure Act, which has in the past been used against journalists to force them to disclose the sources of their information.

De Lille said on Thursday she was among those approached by the Heath Unit for permission to hand over certain documents it received through her office.

However, on advice from her lawyers she was told to advise Heath that the president should make the request to her personally in writing.

The president should also furnish reasons why he wanted the information, especially as Mbeki had already made his decision to exclude Heath from the probe.

De Lille said she had yet to receive a request from the president.

Referring to the letter between herself and Heath, De Lille said on Thursday night that she would have handed it over to the ANC if it had requested it.

She added that the ANC was "using every trick in the book" to divert attention away from probe. 

With acknowledgement to Sapa and News24.