Opposition political parties accused the African National Congress on Monday of trying to bring parliament's watchdog public accounts committee and the probe into the controversial R43-billion arms deal under its control.

The Democratic Alliance's spokesperson for public accounts, Raenette Taljaard, said the investigation was dealt a "major setback" after the intervention of Frene Ginwala, the parliamentary speaker, and the removal of the ANC's study group leader, Andrew Feinstein.

The African National Congress dumped Feinstein as chair of its study group and replaced him with the party's deputy chief whip, Geoff Doidge.

Feinstein was a prominent member of the National Assembly public accounts committee, and - along with the committee's chair, Dr Gavin Woods (of the Inkatha Freedom Party) - led the charge to ensure the executive was accountable to parliament, including on the matter of the multi-billion arms deal.

He was believed to be reconsidering his position in parliament and on the committee.

"I am saddened by it (his demotion)," he said.

"I will need to reconsider my position on the committee and parliament," he said.

He was not prepared to comment further, saying: "I have been told not to talk to the media."

Taljaard said the move could only be interpreted to mean tighter internal political control for the ANC over the arms probe, and over Scopa in general.

"The removal of Feinstein - who incurred the wrath of Minister Essop Pahad last year for his views on the arms deal - is bad news for a committee battling to remain non-partisan and immune to political interference."

She said questions raised by Ginwala - including whether Woods acted beyond his power, and Deputy President Jacob Zuma's letter to the committee - needed to be discussed by parliament soon.

"Procedural wrangling between the various players must not be permitted to obscure or derail the investigation. This must proceed as a matter of urgency," Taljaard said.

In a letter dated January 19 and addressed to Woods, Zuma criticised the committee for "seriously misdirecting itself and arriving at decisions on the arms deal that were not substantiated by any facts".

The United Democratic Movement's spokesperson for public accounts, Gerhard Koornhof, said a danger now existed that the investigation would be "completely diluted and will be controlled by pro-ANC bodies".

"In a clever and calculated move, the ruling ANC is further ensuring that the whole investigation into the arms procurement process falls under its direct control, and that it dictates the conditions under which the investigation continues."

The overseeing role of Scopa in this investigation was being undermined by involving other parliamentary committees, all of whom were chaired by the ANC, he said.

Ginwala has recommended that other parliamentary committees be consulted on the probe.

"Consequently the role and influence of Scopa, the only parliamentary committee under opposition chairmanship, is effectively diminished and limited," Koornhof said.

"It can be expected that the remaining ANC members on this committee will now have to follow explicit orders from the party, or follow the route of Feinstein."

Woods told SABC Radio it would be a loss to the committee if Feinstein left.

With acknowledgement to Sapa and Independent Online.