Acting Defence Minister Phil Goff has asked the air force to assist farmers to feed out hay to stock trapped by snowstorms in Central Otago.

"This is an emergency situation brought about by a one in twenty year event.

"Civilian helicopters in the region don't have the lifting capacity to do the job and with RNZAF helicopters in the region on a training exercise, it makes sense for us to use them to help out.

"Our Defence Forces are frequently called upon in emergencies in New Zealand and in the Pacific, such as following cyclones or floods. Helping out in this situation is an extension of their disaster relief role.

"Headquarters Joint Forces New Zealand is coordinating with the Ministry of Agriculture the involvement of RNZAF helicopters and personnel.

"Four Iroquois are currently exercising in western Southland and Fiordland. Tomorrow morning, they will fly to Central Otago and will spend the day distributing feed to stock trapped by the snowstorms.

"The government appreciates the problem that farmers are facing in the region and hopes that this help will assist them through this critical situation," Mr Goff said.