The chartered-in 22,000–gt Stena Alegra (built 1998) suffered a six-metre gash in its hull above thewaterline when it hit a wharf at Wellington on Tuesday, putting it out ofservice.

Meanwhile, rudder-shaft cracking has been found on the 12,600-gt Aratere (built 1998),which is being repaired in Singapore after losing its propeller in November.

A spokeswoman for operator Interislander said the StenaAlegra accident happened in ''the midst of extreme weather conditions''.