A popular holiday spot near Wellington has been shut off due to serious safety concerns, but the local mayor hopes disappointed holiday-makers will understand.

The Kapiti Coast District Council's closed the Otaki Gorge Road to traffic and pedestrians - blocking access to the Otaki Forks area and Tararua Forest Park.

Contractors clearing debris from slips have discovered much larger cracks above the road and mayor Ross Church says they suspect the whole hillside could be slipping.

"Sadly there's some serious cracks in the hill behind the current minor slip and it looks serious, so it's just got to be checked properly before we can allow people through there," he says.

Mr Church says they know the timing couldn't be worse, but they can't take a risk with public safety.

He hopes they will know more definite information by the end of January but going off current information, it could be closed for months rather than weeks.