Tan Sri Rahim Noor told an official inquiry into the assault that he slapped Mr Anwar for allegedly insulting him.

The former police chief had already admitted assaulting Mr Anwar after his arrest last September on corruption charges.

Frances Harrison reports for BBC News

Describing the incident for the first time, he said that his initial instinct had been to untie Mr Anwar's blindfold, but as he approached he said Mr Anwar referred to him as "the father of dogs".

Lost control

The former police chief says Prime Minister Mahathir was not involved

At that point, he said, he struck out at Mr Anwar. "I lost my cool, I lost my sense of control," he said.

He denied being given instructions from the prime minister or anyone else to beat up Mr Anwar.

"Let me make it clear, my act as referred to was not prompted, abetted, instructed, advised, directed, assisted by anyone else, not even my police officers who helped me, not even the prime minister," he said.

The former police chief said Mr Anwar, who was blinfolded in his prison cell at the time, fell over on a concrete slab.

Under pressure

Mr Rahim Noor resigned last January

Mr Rahim Noor resigned his post in January after an inquiry by Malaysia's attorney general blamed the police for Mr Anwar's beating.

He said that in that split second he could not remember whether he delivered other blows to Mr Anwar because he felt someone pulling him out of the cell.

He said he was under pressure at the time because he said a frightening and chaotic situation prevailed in Kuala Lumpur at the time because of tens of thousands of people taking part in opposition demonstrations.

'Potentially lethal'

Mr Anwar's injuries could have been lethal, doctors say

Mr Rahim Noor told the inquiry he had been considering imposing a curfew in the capital because of intelligence reports that opposition activists were going to set the prime minister's house on fire and occupy the area near the parliament.

Mr Anwar said he was assaulted repeatedly before passing out. Giving testimony last week, he told the independent commission he was punched, karate-chopped and slapped at least seven times until he was bleeding and later passed out unconscious.

Frances Harrison: "There is confusion about what happened"

A government forensic report presented last week said his injuries could have been lethal. It found that the former deputy premier had been "hit by a blunt object at least four times on the head and neck and slapped at least twice".