Key Points:

An investigation into the alleged sex attack on a minimum security prisoner by his notorious double rapist cellmate has been "complicated" by a counter allegation that it was consensual.

Corrections confirmed to NZPA today that police were investigating a rape complaint at Waikeria Prison in Waikato.

"We understand the police investigation has been complicated by the suggestion consensual activities may have taken place," Waikato central regional manager Gavin Dalziel said.

The Sunday News reported today the alleged victim was a middle-class European man in jail on dishonesty offences, including credit card fraud.

It named the alleged attacker as Black Power gangster William Wii Katipa, 41, who is serving preventive detention for raping a woman in front of her two-and-half-year-old daughter.

He had previously been jailed for raping a 13-year-old girl.

The newspaper said the alleged victim had asked to be transferred from Waikeria to nearby lower security Rangipo Prison but was told by prison staff that he was facing more charges and he had to stay at Waikeria.

He learned later -- after the alleged rape -- that there were no more charges.

The minimum security inmate, who claimed he was raped by Katipa on two separate occasions last October, is understood to have been suicidal since the alleged attack.

He has since been transferred to Rangipo.

Mr Dalziel said both prisoners were medium security classification and all procedures and policies were correctly followed.

"We immediately acted on the complaint, police were called and the complainant prisoner was held separately until his transfer from Waikeria. This occurred after outstanding charges had been dealt with."

The alleged victim had also received ACC counselling, he said.

Mr Dalziel said Corrections held the safety of the public paramount.

"While all reasonable efforts are made to ensure prisoner safety, it is inevitable given the nature of prisoners, that risk to individuals can be higher than in the outside world."

Katipa, 39, had already been jailed for the rape of the 13-year-old girl in 2002 when a DNA sample was taken from him and used to convict him of the earlier rape of the young mother in front of her daughter.