Speaking at the annual meeting of the ruling United Malay National Organisation (Umno), he accused Mr Anwar of being behind a plot to take over the government during a period of economic turmoil.

But in spite of widespread speculation to the contrary, he did not use the occasion to announce a snap general election.

Instead, in a speech intended to appeal to Malaysian nationalism, he reiterated his criticism of "ethnic Europeans" he said were intent on re-colonising the country and destroying its economy.

Colonial 'puppet'

In April Mr Anwar was sentenced to six years for corruption

"Prospective colonialists and their puppets in Malaysia are still trying to weaken this country," he said. "Malaysia can only be recolonised over Umno's dead body."

Mr Anwar had been once such "puppet", he told the 2,000 party delegates.

He said Mr Anwar had "used foreigners and the foreign media to support the actions of his supporters in order to topple the government of our country, his country".

"Many among them are of the opinion that Muslims cannot possibly succeed, more so when their skin colour is brown."

'No conspiracy'

In his address, Dr Mahathir dismissed as "nonsense" suggestions that he had conspired to remove Mr Anwar from his post because he had become a political threat.

Larger than life: Dr Mahathir revisited familiar themes of Malaysian nationalism

"On the contrary, I became a victim of a conspiracy to topple me," he said.

Other delegates gave their backing to the prime minister. "Anwar has stabbed us in the back," a representative from Dr Mahathir's home state told assembly.

Dr Mahathir's return to the theme of foreign domination and the attack on his former deputy are being seen as an effort to revive Umno unity ahead of general elections.

The BBC's Frances Harrison reports that the party is still split over the Anwar trial

Speculation had been rife that Dr Mahathir, Asia's longest serving ruler, would announce a date during his speech, but it is still believed that these will be called well before the final date in June next year.

Pre-election campaigning is already underway and many analysts say they expect Dr Mahathir will try to exploit apparent disunity in the opposition whilst pointing to signs of economic recovery.

Fallen heir

The path to Mr Anwar's downfall began at last year's Umno assembly, with the circulation of a booklet to delegates entitled "Fifty Reasons Why Anwar Cannot be Prime Minister".

Kuala Lumpur was rocked by riots following Mr Anwar's arrest and conviction

Once the golden boy of Malaysian politics, the former deputy premier was widely seen as Dr Mahathir's chosen successor.

His arrest last September on charges of corruption and illegal homosexual activities sparked widespread political protest. About 400 members were expelled from Umno for openly supporting Mr Anwar.

He was convicted in April of abusing his office to cover up allegations of illicit sex. He is currently on trial on charges of sodomy which could add a further 20 years to his sentence.

At the trial, which also continued on Friday, a former police chief testified that Special Branch investigations had uncovered firm evidence that Mr Anwar had engaged in sex with another man.

Mohamad Haniff Omar, who was the inspector-general of police until 1993, said he had informed Dr Mahathir at the time.

Mr Anwar's defence lawyer said the evidence was obviously based on hearsay, but the judge overruled his objections.