The cargo vessel which shed dozens of containers on to a world heritage coast leading to scenes of looting and scavenging was overloaded, according to a report.

The discovery was highlighted in a report by the Marine Accident Investigation Branch after it found "discrepancies" in declared weights of containers on board the MSC Napoli contributed to it running aground off the Devon coast in January last year.

Investigators have called for a review of best practice in shipping while claiming that shippers deliberately overload vessels at the expense of safety.

The storm-damaged MSC Napoli - carrying 2318 containers - was grounded a mile off Sidmouth, amid fears she could break up, while being towed to Portland, Dorset.

Hundreds of people from across the country flocked to nearby Branscombe beach to scavenge everything from BMW motorbikes to disposable nappies when dozens of containers washed ashore.

The MAIB in the report on the accident published today says shippers "deliberately under-declare" containers' weights in order to minimise import taxes calculated on cargo weight, to allow the overloading of containers and to keep the declared weight within limits imposed by road or rail transportation.

Data recovered from the Napoli's loading computer indicated that it had arrived or departed from berths or other ports on several occasions on up to 122% of her maximum stress levels.

The MAIB concluded that this, along with the ship's speed and its loading, had caused the vessel to "break her back" as she headed directly into high seas.

The MAIB also felt that the design of the ship and loading capacities had not taken into account the impact of large waves.

"In view of the potential increase in wave loading due to whipping effect, further research is required by classification societies to ensure that the effect is adequately accounted for in ship design and structural analyses," the report says.