BangkokPost.com from Reuters reports Thailand's best known disaster prognosticator said on Wednesday global warming will put Bangkok a metre under water in less than 20 years, adding: "You will need a motorboat instead of a car."

Smith Dharmasaroja, head of Thailand's National Disaster Warning Centre, told the Reuters news agency that rising seas and natural sinking will put Bangkok under water by 2025 - unless work starts now on a huge dyke to protect the capital.

"If nothing is done, Bangkok will be at least 50 centimetres to one metre under water," Reuters quoted Mr Smith as saying during an interview in Bangkok.

Mr Smith gained notoriety 12 years ago when he predicted Thailand was in danger of being hit by a tsunami. Largely dismissed as a crackpot and retired from government service with the Meteorological Department, he was brought back as a disaster expert after the 2004 tsunami, which killed more than 5,000 people in Thailand alone.

The problem, he says, is two-fold.

The city is subsiding at a rate of 10cm per year, partly due to excessive pumping of underground water.

Global warming is causing seas to rise and there is evidence of severe coastal erosion just downstream from Bangkok.

To avert disaster, Smith said, the city needed to construct a massive dyke to protect it from rising seas and increasingly violent storms.

"The system has to be started right now. Otherwise it will be too late to protect our capital city," he said.

Mr Smith, as usual, was scathing when asked about how authorities are facing the threat.

"The government does not pay any attention at all."