They say the police should not have questioned a potential witness, member of parliament Sng Chee Hua, only hours after he was named in court as a participant in a secretly-recorded conversation.

Ms Ummi said she could not remember

The tape reportedly records a discussion with Ummi Hafilda Ali - a key prosecution witness whose allegations form a central part of the case against Mr Anwar.

Mr Sng, who is also vice president of one of Malaysia's ruling coalition parties, allegedly met Ms Ummi in London in June.

Lawyers say the tape supports their argument that she fabricated the tales of Mr Anwar's sexual indiscretions as part of a political conspiracy to topple him.

The BBC's Simon Ingram reports on the latest twist in the Anwar saga

Ms Ummi initially denied the extracts read out in court but later said she could not remember.

Judge Augustine Paul has banned reporting of the transcript and ruled the tape cannot be used as defence evidence unless the person who made it is brought to court.

He refused to condemn the police for questioning Mr Sng on Wednesday.

Anwar Ibrahim's wife Wan Azizah Ismail interviewed on BBC World

But he adjourned the trial to give the defence time to listen to the tape and interview Mr Sng following the police interrogation.

Mr Anwar is on trial on four corruption charges related to allegations he used his position to cover up the claims of sexual misconduct.

Prime Minister Mahathir Mohammad fired Mr Anwar as his deputy and finance minister in September.

Mr Anwar, who also faces another corruption charge and five counts of sodomy, denies all the allegations against him saying they are part of a plot to bring him down.

The role played by the police has come in for critical scrutiny several times during the trial in Kuala Lumpur which began last month.