The ship Hoegh Osaka listed and flooded after being incorrectly loaded, an investigation found.
The Marine Accident Investigation Branch has published a detailed report about the 51,000-tonne vehicle carrier, which was beached deliberately on Bramble Bank on January 3 last year after it left Southampton.
It was carrying 1,400 cars and 105 pieces of construction equipment, but too much cargo had been loaded into the upper decks rather than the lower ones, the report found.
The MAIB has now issued a safety flyer highlighting lessons that need to be learned and issued guidance to the shipping industry.
Steve Clinch, chief inspector of Marine Accidents, said: ‘The MAIB’s investigation found Hoegh Osaka’s stability did not meet the minimum international requirements for ships proceeding to sea.
‘The cargo loading plan had not been adjusted for a change to the ship’s usual journey pattern and the number of vehicles due to be loaded according to the pre-stowage plan was significantly different from that of the final tally.
‘Crucially, the assumed distribution of ballast on board bore no resemblance to reality, which resulted in the ship leaving Southampton with a higher centre of gravity than normal.’
He added: ‘This accident is a stark reminder of what can happen when shortcuts are taken in the interest of expediency.
‘It is therefore imperative that working practices adopted by the car carrier industry ensure that there is always sufficient time and that accurate data is available on completion of cargo operations to enable the stability of such vessels to be properly calculated before departure.’
Hill Head Councillor Arthur Mandry said: ‘It’s obvious and commendable that an investigation has been carried out.
‘As a result of that, potentially there could be changes in practices.’
He added: ‘If the ship had sunk it could have blocked the entrance to Southampton for a considerable period.’