Older prisoners are being "set up to fail" after they are released, campaigners say.
They face a lack of adequate provision to meet their health and social care needs, it was claimed.
In a joint report the Prison Reform Trust and Restore Support Network said people aged 60 and over are the fastest-growing age group in the prison system.
As of March there were nearly 12,600 inmates aged at least 50 behind bars in England and Wales, meaning they accounted for just under 15% of the total prison population.
Interviews were carried out with 14 people aged over 50 about their lives after prison.
The report said:
:: Nine felt that the prison had not adequately prepared them for release
:: Nine said they needed help with education, training or employment but only one person said that they had been given help.
:: Ten of the 14 said they felt socially isolated.
Juliet Lyon, director of the Prison Reform Trust, said: "This report shows that for many older people in prison getting through their sentence is only the beginning.
"Poor health, no home or job, isolation and neglect paint a bleak picture on release.
"It's clear that with such wide variation in standards of treatment, care and resettlement, a national strategy is needed without further delay. "
Stuart Ware, chief executive of the Restore Support Network, said: "This timely report highlights that unless the Care Act is fully implemented in all our prisons, there will continue to be an escalation of needs when people are released from prison, along with increased cost of care in the community that will have to be borne by local authorities."
A Ministry of Justice spokeswoman said: "All prisoners receive a resettlement plan, including support to find somewhere to live following release and access to the specialist services they need.
"In addition older prisoners will often have greater healthcare needs and prisons work closely with the NHS and local government to provide care for older prisoners.
"A number of prisons also make specific provisions through dedicated wings and units, adapting the regime according to need."