A leaked government report predicts rising sea levels is putting hundreds of thousands of homes at risk.

The Ministry for the Environment report, delivered to the Government in April, shows homes in Canterbury and Hawke's Bay are most at risk.

The report warns sea levels could rise up to 40 centimetres by 2050.

Climate scientist Jim Salinger told Mike Hosking those numbers aren't alarmist.

"What was once a one in 20 event, this is king tides now is occurring two thirds of the time. What that means is your king tides are even higher."

He said the government's chequebook will have to come out if it's to protect against rising tides.

"If you look at places like Holland who have built dikes that's a huge amount of investments, you are talking trillions of dollars."

LISTEN ABOVE AS JIM SALINGER SPEAKS WITH MIKE HOSKING