Cape Town - The Scorpions on Monday served subpoenas - relating to their investigation into the arms deal - on MPs from at least four political parties, it emerged on Wednesday.

However, the subpoenas were later withdrawn after national assembly Speaker Dr Frene Ginwala raised concerns about parliamentary privilege and the fact that these were served on MPs in parliament without her permission, political party chief whips were told on Wednesday.

Among those MPs who received subpoenas to appear as witnesses were Dirk Bakker and Hennie Smit from the NNP.

Smit serves on parliament's defence committee, and Bakker an alternate.

They were among MPs to be interviewed on their knowledge and understanding of the role and function of the defence committee, with regard to the drafting and approval of the White Paper on Defence and the Defence Review.

They were also to be questioned on their understanding of the arms acquisition process and the role parliament's committees on defence played in the process, if any.

Bakker confirmed he had received the subpoena in his office on Monday and was to have appeared before the Scorpions on Wednesday afternoon to be interviewed.

However, he said he received a phone call from the Scorpions on Tuesday saying the subpoena had been withdrawn. "I was told it would be rescheduled for a later stage."

UDM president Bantu Holomisa on Wednesday raised concerns about the Speaker's role in the revoked subpoenas, and said it amounted to interference in the arms probe.

"The curious part of it is that it involved Madame Speaker. What the hell has it got to do with her?"

He said the law enforcement agencies should be left to investigate the arms deal and that their investigation should run its course.

Ginwala was not immediately available for comment.

However, DA Chief Whip Douglas Gibson said he believed Ginwala had acted correctly as she was there to protect MPs.

Gibson said he believed parliamentary privilege did relate to committee proceedings, and that in this respect the MPs could not be expected to give information and were immune from civil and criminal proceedings.

He said it appeared all the MPs had been prepared to co-operate and it was not clear why they should have been subpoenaed.

"I don't understand why people were subpoenaed. No one had refused. As far as I am aware not one of them was accused of anything.

"Madam Speaker was quite right."

Gibson said he was not aware of any DA MPs being subpoenaed. It was not immediately clear how many MPs were in fact subpoenaed.

With acknowledgement to Sapa and News24.