Calderdale has lost more than 100 its care home beds over the last five years, figures reveal.
Charity Age UK has warned of emerging "care deserts" in parts of the country, leaving older people without access to proper care.
Analysis of Care Quality Commission data shows that Calderdale has lost 127 care home beds since 2014.
There are now 1,353 in the area - a fall of nine per cent .
Over the same period, the number of people aged 75 and older in Calderdale has increased by nine per cent, from 15,900 in 2014, to an estimated 17,300 this year.
Across England, the number of beds has increased by 1.4 per cent, rising to 407,058.
But 75 local authority areas have lost almost 10,000 beds between them, prompting concerns about regional inequalities across the adult social care sector.
Retirement mortgage company Responsible Life, which produced the research, said the results reveal "a postcode lottery unfolding".
Managing director Steve Wilkie said: "If this trend isn't reversed, it is going to get even tougher to access care in certain areas in the coming years.
"For some, it will mean a lack of availability, and subsequently higher costs, and will force them to delay accessing the right care at the right time. Others may feel they are better off financially paying for assistance at home.
"The danger is that some retirees will inevitably choose to remain in homes that do not meet their requirements."
The availability of beds in care homes varies considerably in different parts of England, according to Responsible Life's analysis.
Middlesbrough, in the North East, has the best, with 15.6 care home beds for every 100 residents aged 75 and older, while Westminster has the worst at just 2.5.
In Calderdale, there are 7.8 care home beds for every 100 older residents. The national average is 8.5.
Age UK has criticised Government handling of adult social care, and said the system is "chaotic and broken" after years of underfunding.
Charity director Caroline Abrahams said: "If the awful situation set out in this report doesn't persuade our Government to finally get a grip and take action, I don't know what will."
The Department of Health and Social Care said it would set out plans to reform the social care system "at the earliest opportunity".
A spokesperson said: "People must have access to high quality care that meets their needs. Local authorities have a duty to ensure people receive appropriate care and support.
"We have given them access to up to £3.9 billion more dedicated funding for adult social care this year, and a further £410 million is available for adults and children's services."