Any changes to the powers and functions of the Scorpions should be carried out by parliament, as that institution created the investigating unit, Democratic Alliance leader Tony Leon said on Thursday.

Writing in his weekly newsletter, Leon said if there was a case for redefining the Scorpions' mandate, that task should be performed by parliament, not the executive.

The Scorpions and the Special Investigating Unit had both been touted by President Thabo Mbeki and the African National Congress as evidence of the government's commitment to fighting crime and corruption, said Leon.

"But as soon as these institutions began digging in the president's garden, the ANC hit the panic button.

How is it that every time the hammer of justice is about to fall, ANC leaders suddenly discover a whole lot of jurisdictional facts and procedural errors and questionable motives that must prevent investigators from doing their jobs?" Leon asked.

It was announced earlier this week that the corruption-busting unit is being "reviewed".

Safety and Security Minister Charles Nqakula said the review was about redefining the Scorpions' mandate, and not about disbanding it.

Leon said when the Scorpions were created, the Democratic Alliance warned the unit could become a tool of political harassment.

With acknowledgement to the Cape Times.