MALAYSIA'S ''dangerous'' decline is fuelled by incompetent politicians, Thailand is dogged by corruption and a ''very erratic'' crown prince, Japan is a ''big fat loser'' and India is ''stupid''.

So say some of Singapore's highest-ranking officials, according to leaked US State Department cables that are likely to spark intense political controversy in the region.

The cables, leaked exclusively to The Sunday Age by WikiLeaks, detail the content of separate meetings between senior US officials and Singapore's foreign affairs chiefs Peter Ho, Bilahari Kausikan and Tommy Koh.

The trio, who at the time of the 2008 and 2009 cables occupied some of the most senior positions in Singapore's Foreign Affairs Ministry, all give US officials damning assessments of Malaysia.

According to one cable detailing a meeting in September 2008, Mr Kausikan told US Deputy Secretary of Defence for East Asia David Sedney that ''the situation in neighbouring Malaysia is confused and dangerous'', fuelled by a ''distinct possibility of racial conflict'' that could see ethnic Chinese ''flee'' Malaysia and ''overwhelm'' Singapore.