Calderdale council is aiming to deliver homes for four times as many people by 2033 than projections from the Office for National Statistics say are needed based on expected population growth levels.
The Labour-run authority, whose Local Plan setting out its development blueprint for the next 15 years is being examined by government inspectors, proposes to build 997 homes a year on average.
This is based on analysis by consultancy firm Turley which "deliberately allows for increased in-migration to grow the labour force rather than simply continuing the demographic trends recorded locally in Calderdale".
It suggests that official household projections take no account of local development aims, policies on growth, or other economic factors that could impact the population.
And it concludes that the population in the district could grow by as much as 19,320 by 2033, compared with the increase of 4,221 projected by the ONS.
The council has defended its approach, saying Calderdale has only delivered half the new homes needed in recent years, meaning that "in some areas the housing stock is not fit for purpose, especially for growing families"
But residents Amanda Tattersall, who is participating in the Local Plan consultation, and Lyndsey Ashton, who is campaigning against hundreds of homes being built in the village of Greetland, have questioned the analysis that underpins the document.
Of the 15,000 homes that need to be built to meet the Local Plan requirements, nearly 7,000 will need to be built on protected Green Belt land. Campaigners say brownfield sites which have already been used should be prioritised before building on the Green Belt.
Last month, leading rural charity CPRE said the nation's green belt land is facing "extreme and sustained pressure" amid a big rise in the number of homes due to be built in the protected areas in the last decade.
Its annual State of Greenbelt 2021 report said that there are currently 257,944 homes proposed to be built on land removed from the green belt – nearly five times as many as in 2013.
And its analysis suggests the new formula to determine housing supply proposed by the Government could lead to at least a 35 per cent increase in housing on the Green Belt.
The Government - which has a target of building 300,000 homes a year - revised its planning formula for calculating housing need in December so that more homes would be built in major cities in the North and Midlands.
It came after a huge backlash from Conservative MPs regarding plans for the formula – dubbed a “mutant algorithm” – which would have focused housing in high value and rural areas in the South East.
The new algorithm proposes a cities and urban centres uplift, whereby 20 of England’s largest urban areas will have their housing targets increased by 35 per cent.
Mrs Ashton, a stay-at-home mother who helped set up Greetland Pressure Group, is worried about the impact of a proposed large housing development of 600 homes in her village and what this would mean for air pollution around local schools.
She said: "I knew that I had to do something to save our natural heritage. I have rallied thousands of supporters, organised protest walks, written planning objections, given verbal evidence at hearings. None of which I’d ever done before.
"Housing should not be allocated in locations that best serve developer return in investment; home building should and must be sustainable.
"My house backs onto the public right of way and the river side walk, and I have never seen the walk as popular as it has been over the course of the pandemic. It has offered a physical and mental lifeline to residents during an incredibly hard time.
"The pandemic itself is thought to have been caused by human encroachment onto the natural world. How many warnings will we ignore before it is too late? We are part of nature, we belong to nature, and we are at the mercy of nature. We cannot thrive if we try to exist in a disparate bubble, apart from that which our survival is so fundamentally reliant on."
Calderdale Council’s Corporate Lead for Planning, Richard Seaman, said: “In recent years Calderdale has delivered about half the number of new homes that are needed.
"Failing to plan effectively for housing has many negative consequences and the COVID pandemic have brought a number of these into particularly sharp focus.
"In some areas the housing stock is not fit for purpose, especially for growing families; many people are struggling to find homes that are affordable; and we also need to ensure that there are sufficient homes to meet the needs of growing businesses in Calderdale.
“Our draft Local Plan requires an average of 997 new homes to be built annually until 2033.
"This figure takes into account feedback from the Planning Inspector after the first stage of hearings in 2019 and a detailed analysis that was discussed in front of the Inspector during the autumn 2020 Local Plan hearings.
"The Council is therefore confident that it is pursuing an approach that is consistent with the Government’s target to build 300,000 homes annually.
“Calderdale is tightly constrained by a Green Belt that has remained largely unaffected by development for many decades.
"The Local Plan has prioritised brownfield and other land in urban areas; however, It is simply not possible to meet our needs without some loss of Green Belt.
"It is important to put this in context though – about 98 per cent of the Green Belt will remain free of development."
Mrs Ashton said that while 98 per cent of the Green Belt in Calderdale will remain, "this means nothing to the residents that currently stand to lose practically all of the Green Belt that characterises their rural villages".
She added: "It is crucial that local residents have access to open space, for their well-being, and this could be achieved if the council better spread development out across the borough, specifically in the areas that are most in need of affordable housing, instead of concentrating new homes in areas that developers most prefer."