A cruise ship heading to Auckland in New Zealand rolled sharply in rough seas overnight, causing many passengers to need medical treatment.

A spokesman for P&O Cruises said the Pacific Sun was affected by the severe weather conditions that swept across the country.

The ship was experiencing seven meter swells and 50 knot winds when it rolled sharply just before 8pm on Weds.

The ship is currently still in the water as it has been delayed due to the bad weather. There are 1,732 passengers and 671 crew members aboard the vessel.

Families of passengers seeking more information can call 0800 951 200 according to The Age.