The Japanese government has issued an urgent warning over the catastrophic damage which could be caused by an impending megaquake.

Experts now believe there is an 80 per cent chance of a magnitude nine tremor occurring in the Nankai Trough off Japan’s Pacific coast within the next 30 years.

New government estimates show that this disaster would kill 300,000 in the worst-case scenario.

This includes 215,000 deaths caused by tsunami waves exceeding 30m (98ft) in some areas.

The Nankai Trough is a deep ocean trench formed by the boundary of two tectonic plates, which is hit by a megaquake once every 100 to 200 years.

In the deadliest scenario, the report predicts that 2.35million buildings would be destroyed by collapses, flooding and fires.

The destruction would cause damage worth £1.44trillion (214.2trillion yen) and create 12.3million evacuees.

That is the equivalent of displacing 10 per cent of the Japanese population within a week of the earthquake.