More than 1,000 new homes could be built on derelict or previously used land in Calderdale, according to greenbelt campaigners.
The Campaign to Protect Rural England says there is enough vacant brownfield sites in towns and cities across England and Wales to build more than one million new homes – two thirds of which could be delivered within five years.
It has called on the government to force councils to prioritise brownfield development instead of building homes on green spaces.
In Calderdale, the CPRE says there is capacity to build 1,347 homes across 27 sites.
Of these, 89 per cent, or 1,196 homes, could be delivered within five years.
Rebecca Pullinger, planning campaigner at the CPRE, said: "Building on brownfield land presents a fantastic opportunity to simultaneously remove local eyesores and breathe new life into areas crying out for regeneration.
"It will help to limit the amount of countryside lost to development, and build more homes in areas where people want to live, with infrastructure, amenities and services already in place."
The CPRE analysed Calderdale Borough Council's Brownfield Land Register, which lists sites that the council says are suitable for development.
A brownfield site is defined as land that "is or was occupied by a permanent structure".
However, the CPRE says that confusion over the definition could mean councils are leaving potential sites off their registers.
This could include land that is already in use, but could be altered to make space for housing, such as car parks.
More than 120,000 potential new homes have been added to registers in England in the last year.
In Calderdale, 906 new homes were added last year , 766 of which have been assessed as being deliverable within five years.
The brownfield sites now on the register cover a combined area of 67 acres.
This would give an average housing density of 20 homes per acre – above the national average of 17.
The Local Government Association said councils had already given hundreds of thousands of homes planning permission which have yet to be built.
It called for better resourcing for council planning departments, to ensure developers build homes as quickly as possible.
The Housing Minister, Kit Malthouse, said: “This Government is committed to building the homes our country needs while still leaving the environment in a better state than we found it.
“We’re encouraging planners to prioritise building on brownfield land and working with local authorities to ensure sensible decisions are made on where homes get built.”