The result of Saturday's election is not in doubt after the ruling party's unbroken 36-year rule was extended when opposition parties decided not to field candidates in 55 of 84 seats.

"The misuse of defamation suits by PAP leaders has contributed to a climate of self-censorship in Singapore and restricted the right of those Singaporeans with dissenting opinions to participate freely and fully in public life," London-based Amnesty said in statement.

Chee Soon Juan, leader of the Singapore Democratic Party, fell foul of Prime Minister Goh Chok Tong and Senior Minister Lee Kuan Yew by suggesting S$17 billion (US$9.3 billion) in taxpayers' money had been lent to former Indonesian President Suharto.

The PAP said the loan never went ahead. Goh and Lee have threatened to sue Chee for defamation but say they use the courts only to defend their reputations at home and abroad.

Amnesty noted a pattern of what it called "politically motivated libel suits".

It cited actions in the 1997 election against Workers' Party candidate Tang Liang Hong when PAP leaders won damages of US$5.5 million, which were reduced on appeal to US$2.3 million.

Also in 1997, suits were filed against then Workers' Party leader J.B. Jeyaretnam which ultimately led to his bankruptcy.

Amnesty said it "remains gravely concerned that defamation suits have not solely been motivated by a legitimate desire to defend reputation but have been directed selectively at those considered politically 'unacceptable' by the PAP".