As the deadline passed for candidates to nominate, electoral officials said opposition parties had fielded just 29 valid candidates for the 84 seats up for grabs.

The remaining 55 seats for which the PAP is the sole challenger - well over half of those in the next parliament - will not be contested on polling day, set for November 3.

The walkover will enable the PAP to continue its unbroken run in office, which stretches back to independence in 1965.

Prime Minister Goh Chok Tong said the forthcoming poll would be his last as prime minister, echoing comments he has made that he would like to stand aside before the coming five-year mandate expires in 2007. He took office in November 1990.

This year, Mr Goh endorsed Deputy Prime Minister Lee Hsien Loong, son of Senior Minister Lee Kuan Yew, as the man he would like to succeed him.

The PAP last faced a full contest in 1988. At the two most recent national polls, in 1991 and 1997, opposition parties put up candidates for fewer than half of the seats on offer, ensuring the election was over before campaigning started.

Mr Goh called this year's snap poll 10 months early as the trade-reliant city-state was battered by the worst recession in more than 30 years.

A week before Parliament was dissolved, the Government announced an emergency package of measures worth S$11.3 billion to aid businesses and workers.

"We're going to be in for a deep recession," Mr Goh said yesterday after filing his nomination papers. "I just want to get the election through and get back to work."

Later, he said he planned to play an active role in economic policy-making after he stood down as prime minister.

Opposition parties have long failed to make much headway in Singapore. Observers say the Government's track record in improving people's standard of living has bolstered the PAP's remarkable electoral appeal.

In previous campaigns, the ruling party made it clear voters who returned opposition candidates were unlikely to have their housing estates upgraded, a tactic that may hold back the value of their properties.

Opposition campaigners argue that the electoral rules are stacked against them. Just before the present campaign was announced, the Elections Department rearranged the electoral map, triggering charges of gerrymandering from opposition MPs.

The opposition's showing would have been stronger yesterday, but five Workers' Party candidates who attempted to register to fight the Aljunied multi-member seat were disqualified for failing to fill out their paperwork correctly.

Senior Minister Lee - Singapore's first prime minister - said even though the PAP remained a potent force, it would not win every seat this year. In 1997, the opposition claimed two elected seats.

Dressed in the PAP's trademark white - meant as a symbol of incorruptibility - Mr Lee said: "I won't be having a chance to vote because I'm in Tangjong Pagar [his own uncontested constituency] . . .

"I think that some of them [voters] would feel that they've missed a chance to express grievances."

Mr Lee, 77, said he wanted to run again in 2007 if he were able. But he added: "I am a little uneasy, because the next time I may not be here and there could be a contest. I look around at my [constituency] team and only one of them has had a contest."