Prime Minister Bill English is dropping planned trips to Waikanae and Queenstown today and heading to Christchurch's fires instead.

English was to visit the opening of a new road from McKays Crossing to Peka Peka in Waikanae, the Five Mile Development in Queenstown and the Kawarau Falls Bridge Project in Frankton.

A massive emergency response is under way in Christchurch where a ferocious wildfire has burned more than 1800ha in the Port Hills.