South Africa's main opposition has called for controversial crime intelligence chief Richard Mdluli to be suspended, amid allegations of political interference.
He was moved to another department on Wednesday, but the Democratic Alliance has said this is not enough.
He has accused senior members of the police service of trying to oust him.
Mr Mdluli is said to be a close ally of President Jacob Zuma, who is facing a battle to keep his job.
BBC Africa correspondent Andrew Harding says the real concern is the growing politicisation of the police, and above all, the prosecution services - and the clear suspicion that they are being used by South Africa's feuding political elites to spy on each other, settle scores, and influence the ANC leadership battles and President Zuma's bid for a second term.
Mr Mdluli was suspended last year to face a murder charge, but was reinstated when this and corruption charges were dropped.
Police Minister Nathi Mthethwa told MPs on Wednesday that Mr Mdluli's move to another division was so that allegations of political interference could be probed.
Mr Mthethwa said the investigation would centre on a letter Mr Mdluli wrote alleging there were senior members of the police trying to oust him from office.
The letter was allegedly written to the police minister, the current police chief and Mr Zuma, who became president in 2009.
It allegedly accuses other senior police officers of planning Mr Mdluli's "downfall".
"I have instituted a task team, led by the state law adviser, to investigate such allegations, because they are so serious as to suggest the meddling of policing functions in politics," Mr Mthethwa said in parliament.
Last September, Mr Mdluli was charged and arrested for corruption by South Africa's anti-graft unit, known as the Hawks, after allegedly raiding a police intelligence fund for his personal use.
These charges were withdrawn in December.
He was suspended as crime intelligence boss in February 2012 and reinstated the following month.
The DA said the "shifting" of Mr Mdluli to another department within the police did not address the problems, given the serious allegations still facing Mr Mdluli.
"Numerous questions remain as to the circumstances surrounding his reinstatement in the first instance," DA parliamentary leader Lindiwe Mazibuko said after Mr Mthethwa's announcement.
"All of the available evidence suggests that Richard Mdluli is not fit to serve in any part of the police service or criminal justice system," she added.
Ahead of elections in 2009, the ruling African National Congress divided into rival factions, often using state security agencies, including the police and intelligence services, to try to eliminate rivals.
Mr Zuma, who ran the ANC's intelligence wing in exile during the fight against apartheid rule, is facing criticism from some within his party, who want to replace him.
The ANC is due to decide in December whether to retain him as its leader in the next election, scheduled for 2014.
Critics of Mr Zuma allege that he interfered to get Mr Mdluli re-appointed so he could help him spy on his opponents as the succession battle heats up.
In March, a court ruled that the decision to drop corruption charges against President Zuma - just weeks before the 2009 election - can be reviewed. It was dropped following allegations of political interference in the case.
Another powerful ally of President Zuma, former police chief Gen Bheki Cele, was suspended in October to allow an investigation into allegations of corruption.