Tan Sri Rahim Noor made the admission to a royal commission investigating Mr Anwar's treatment during his detention.

His lawyer, Teh Poh Teik, told the inquiry that his client had instructed him to admit the attack.

BBC Correspondent Frances Harrison: Police chief alleges provocation

Doctors have testified to the inquiry that Mr Anwar's injuries could have been fatal.

The lawyer said Mr Anwar had provoked the beating by insulting Tan Sri Rahim Noor - a charge Mr Anwar denies.

Mr Anwar was arrested last September on sex and corruption charges. He denies the accusations, saying they are politically motivated.

Frances Harrison: Doctors said the beating could have been lethal

The former deputy prime minister says he was beaten unconscious in police cells hours after his arrest.

He has previously accused the former police chief of being involved in the attack.

Mr Anwar says he was blindfolded during the attack but learned from junior officers that the police chief was responsible.

On hearing the admission Mr Anwar said he was stunned, adding: "So I was right all along".

Ex-police chief: First admission

Mr Anwar's wife, Dr Wan Azizah, said she was relieved the assailant admitted the attack, but added that the role of the Prime Minister Dr Mahathir Mohamad should be questioned since he was home affairs minister at the time of the assault, with overall responsibility for the police.

"The whole episode of injustice has galvanised people," she said.

Tan Sri Rahim Noor resigned as Police Inspector-General in January over speculation that he was responsible for attacking Mr Anwar.

He resigned saying he took overall responsibilty for what went wrong in his force.

But it is the first time that he has actually admitted carrying out the assault.