The battle over the R500-million police headquarters lease took a dramatic new turn when news broke that officers from the police's Crime Intelligence Unit illegally raided the office of the Public Protector.

Police spokesman McIntosh Polela described the incursion as "an operation that was not sanctioned by the police".

The raid is believed to have been provoked by a report by Public Protector Thuli Madonsela in which she said that national police commissioner Bheki Cele's conduct in respect of the lease was "improper and unlawful".

Madonsela's spokesman, Kgalalelo Masibi, said two plain-clothes police officers, a man and a woman, arrived at the Public Protector's office unannounced soon after noon on Wednesday.

They identified themselves and said they were from the police's counter-intelligence unit and had been sent to search the offices by a their commanding officer, whom Masibi would not name.

But Masibi conceded that the two said they wanted to ascertain whether documents published in the Sunday Times formed part of Madonsela's report.

"After consulting internally, the Public Protector decided to give the officers a list of the documents used in the investigation, but not the actual documents," Masibi said.

Madonsela is said to be concerned about the incursion and will take up the matter with Cele.

But police spokesman Polela said the police's top brass "condemned" the incursion.

"We didn't sanction it and are launching an investigation to deal with the people responsible".

Three insiders told The Times the two intelligence officers "broke every rule in the police book", and that they believed "underhand" activities were going on.

The officials, who spoke on condition of anonymity, said the officers did not have a search warrant.

Said one senior official: "This is highly suspicious and raises some serious questions. It was clearly not authorised, so the question is: Who is behind this and what exactly were they looking for?"

Said another: "They were not allowed to search and left without any documents. The Public Protector's staff were too sharp for them."

In another twist, The Times has learnt that the cellphones of key contributors to Madonsela's report - as well as those of a number of senior staff at police headquarters to whom the sources have been linked - are being illegally tapped.

A high-ranking police officer interviewed by Madonsela said: "I have been informed that my phone and those of my colleagues are being tapped. I don't know what they want. The truth is out now."

Polela, however, said he knew nothing of this.

"We need to emphasise that we are concerned that it is going to be seen as an act of intimidation of the office of the Public Protector, and we need to put it on record that we respect and support the office of the Public Protector," he said.

"The belief is that they were looking for documents to which Cele was refused access during the investigation by the Public Protector."

In his response to Madonsela's draft report, Cele said several requests to her office to obtain documents used in her investigation were rejected.

Labelling Madonsela's investigation as "fatally flawed", Cele said he had been "denied the right to be heard" and had "suffered material prejudice".

He said Madonsela refused to give him any documents relevant to her findings, and refused to disclose the identity of any witnesses or disclose any of their statements. He said she did not give him enough time to respond to allegations.

One of the documents in Madonsela's possession, said a police official, is a legal opinion Madonsela obtained from an independent law firm regarding the legality of the lease the police signed with businessman Roux Shabangu.

Polela said the incursion was "very contentious" and could be seen as an act of intimidation, but he insisted that police management would act against those involved.

"The members acted outside their mandate, hence appropriate action is being instituted accordingly," said Polela.

"A stern position is going to be taken to send a clear message that members of the police cannot be seen to do as they please."

The abortive "raid" took place a day before the cabinet announced that Justice Minister Jeff Radebe and Presidency director-general Cassius Lubisi had been told to "make sense" of Madonsela's report before acting on it, and to meet Madonsela without delay.

Madonsela said that Public Works Minister Gwen Mahlangu-Nkabinde had also acted improperly towards the lease, which was therefore invalid and should be cancelled.

Government spokesman Jimmy Manyi said Radebe and Lubisi would discuss the report with Madonsela to iron out "issues of protocol and procedure".

"After the engagement of the report, the cabinet will pronounce [on] whether it is accepting or rejecting [the report]," Manyi said.

He denied that this was an attempt to undermine the Public Protector or water-down her report.

Trade union federation Cosatu said Madonsela's office was "a cornerstone of our democracy" and it was "outraged" by the incursion.

"It is a last resort for citizens who have failed to receive justice from the state and for whistle-blowers who want to expose crime and corruption. Any doubt as to the independence of the office could deter people from lodging their complaints and jeopardise its work," said spokesman Patrick Craven.

Opposition parties condemned the raid, saying it suggested that the police were being used to wreak political revenge.

DA spokesman Lindiwe Mazibuko said the party will asked Police Minister Nathi Mthethwa to institute an inquiry.

"This kind of intimidation is typical of authoritarian states that abuse the police for the purposes of protecting powerful elites rather than protecting the public," she said.

Freedom Front Plus spokesman Pieter Groenewald said the "raid" was an attack on democracy.

"It is difficult to believe the raid took place without the knowledge of General Cele. This action shows he should be suspended immediately." - Additional reporting Thabo Mokone