P&O Cruises' Pacific Sun has been affected by the severe weather conditions that have swept across the region.

The ship, which was about 600km north of Auckland, was experiencing 7 metre swells and 50 knot winds when it rolled sharply just before 8 pm last night.

As a result of the ship's sudden movement, approximately 40 passengers were seen and treated by the onboard medical staff.

Pacific Sun has two doctors and three nurses onboard who are highly trained.

"I would like to assure the friends and families of our passengers that they are in good care onboard the ship," a P&O Cruises spokesperson said.

The ship, which was due to return to Auckland this morning, has been delayed by at least 24 hours due to the bad weather.

The ship is carrying 1732 passengers and 671 crew. She was on her return from an eight day cruise in the South Pacific.

For families of passengers seeking more information, please call:

New Zealand 0800 951 200 and Australia 13 24 69.