KUALA LUMPUR, Malaysia (Reuters) -- Malaysia's sacked deputy prime minister Anwar Ibrahim on Monday sued Prime Minister Mahathir Mohamad for slander, claiming 100 million ringgit ($26 million) in damages.

Anwar's lawyers filed a writ of summons at the capital's High Court accusing Mahathir of slandering his former deputy during a news conference on September 22, 1998.

Mahathir sacked Anwar as deputy prime minister and finance minister on September 2.

At the September 22 news conference, Mahathir detailed for the world media what he said were sexual acts that prompted him to sack his deputy.

"Datuk Seri Anwar has been brought to international odium and contempt," lawyer Karpal Singh, whose law firm filed the writ of summons, said in a statement. The suit also seeks an injunction barring Mahathir from repeating the accusations.

Karpal said Anwar had decided to initiate defamation proceedings against Mahathir to clear his name after the judge in his High Court trial recently expunged all evidence relating to alleged sexual misconduct given by prosecution witnesses during the first two-and-a-half months of the trial.

The criminal trial at the High Court, which adjourned on January 14 for the Muslim holiday Eid al-Fitr, was to resume on Tuesday.

Anwar has been in custody since masked commandos broke into his suburban home on September 20 and arrested him, hours after he led 30,000 demonstrators through the streets of the capital calling on Mahathir to step down after 17 years in power.

He was first held in federal police headquarters in the capital under the Internal Security Act, which allows indefinite detention without trial. Authorities said he had been arrested to prevent a breakdown of security.

He has pleaded not guilty to five charges each of sodomy and corruption, and said he was the victim of a political conspiracy.

Among the evidence thrown out by the judge was a mattress, which the prosecution said was stained by Anwar's semen, and statements by witnesses saying he had sodomized his former driver.

Because the judge has ruled that all evidence relating to alleged sexual misconduct is now irrelevant, the defense cannot use witnesses to rebut the accusations if the judge calls on Anwar to put on a defense.

"Justice demands that Datuk Seri Anwar not be cribbed, cabined and confined in his endeavour to clear his name," Karpal said.

It was the third suit brought by Anwar against his former mentor.

In November, he sued Mahathir for sacking him, saying only Malaysia's king could dismiss a minister. The High Court dismissed that suit, and Anwar is appealing.

On January 8, Anwar sued Mahathir for injuries he suffered in police custody in September after being arrested.

Anwar appeared in court in late September with a black eye and said he had been beaten while in police custody. Earlier this month, the federal police chief quit after the attorney-general said police were responsible for Anwar's injuries.

Karpal said Anwar also intended to file defamation suits against an international television broadcaster, an international magazine and a local newspaper for printing the allegations that Mahathir made at the September 22 news conference.

Anwar's case has exposed deep divisions within Mahathir's party and unleashed a flood of sordid accusations in normally staid Malaysia.

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