Search and rescue staff have suspended a land search for a man who fell off a tanker in Wellington Harbour on Monday afternoon.

The Wellington Coast Guard and police have spent the day scouring the harbour's coastline as well as searching the waters of the harbour.

Search and rescue spokeswoman Jo Holden says they are scaling down the search, unless new information comes to light.

She is not optimistic about finding the man alive, given the bitterly cold waters and the time which has passed since he went overboard.