A think tank has called for more homes on greenbelt land around Bristol and Bath.
The Centre for Cities says building on greenbelt is the only way of addressing the region's growing housing crisis.
Alexandra Jones, from the think tank, said: "About 4,300 houses could be built on brownfield land - clearly that's nowhere near what's needed."
The Metro Mayor for the west will have the power to decide housing policy when he or she is elected in May.
Ms Jones, from the independent organisation, added that greenbelt takes up half the land in South Gloucestershire and two thirds of land in the Bath and North East Somerset Council area.
Three local councils which have signed up to the Metro Mayor model have all pledged to increase the number of new homes being built.
The aim is to build another 85,000 homes in the next 20 years which is the equivalent of building two cities the size of Bath.
In October, the government backed a £1bn devolution agreement to Bristol City Council, Bath and North East Somerset Council and South Gloucestershire Council.
The agreement involves creating a Metro Mayor who would make key decisions on major areas such as housing, jobs and roads.