His dark vision included thousands of desperate refugees flooding into the prosperous city-state, foreign investment drying up, and pirate attacks on ships spiralling out of control.

"These scenarios are not predictions," Mr Goh told his teenage audience at the prestigious Raffles Institution. "They are a sample of possible futures we could face. Our actual future could very well be a nastier scenario," he said.

The Prime Minister's warning is the latest in a series of pointed speeches by political leaders to the electorate and would-be voters that Singapore must maintain its internal cohesion to help counter external pressures.

Mr Goh's speech Apr 12 was made against the backdrop of the fast-deteriorating political situation in Indonesia, and political tensions in neighbouring Malaysia, where opposition to Prime Minister Mahathir Mohamad appears to be rising. Singapore is increasingly concerned about both.

The negative scenario is further darkened by the sharp slowdown in the US and Japanese economies, which is already hitting growth in Singapore and other Asian economies.

"Singapore may not fall under communist control, but it can come under a bad democratically elected government," Mr Goh said. "If you look at leaders elections have thrown up elsewhere, you will see that the results were often dismal."

To drive his message home, Mr Goh outlined two scenarios, dubbed "Booming Asia" and "Region in Difficulties". Even under the more benign projection, characterised by stability across the Asia-Pacific region, Mr Goh warned that the failure of government resolve may allow income disparities to balloon, polarising social groups.

The second, "nastier scenario" painted a region in disarray.

"China faces difficulties in restructuring its economy. Japan remains stuck in low growth and South Korea stalls. Southeast Asian countries are laden with debt and gripped by political crises. There is strife in some countries," said Mr Goh. "The region becomes unstable. Illegal immigrants flood Singapore looking for jobs and food. Piracy in the surrounding waters increases."

The Prime Minister must call a general election sometime before August 2002. While every poll since the 1960s has been dominated by Mr Goh's Peoples Action Party, and its victory is assured next time, the government campaigns hard to ensure its electoral popularity is sustained.

"My purpose in painting the scenarios is to tell you not to extrapolate the current state of peace and prosperity in a straight line," said Mr Goh, "and to set you thinking about sudden, disruptive changes to your life."

The teenagers - labelled the "Millennium Generation" by Mr Goh - were urged to balance a commitment to personal development with the country's wider interests.