There are now more than 200 prisoners aged 80 or over, with at least ten in their 90s and many have complex medical and social needs.
The increase in elderly inmates has been put down to rising number of paedophiles being convicted for historic sex offences.
But there are also an increasing number of elderly prisoners who were jailed when they were younger, but are serving lengthy sentences or whole life terms.
The over 60s are the fastest growing age group in prison, but there is mounting concern that many jails are not suitable to deal with their specific needs.
Peter Dawson, director of the Prison Reform Trust said: "An increasingly elderly and frail prison population creates huge challenges for a prison system already struggling to cope.
"A system designed for fit, young men means that many are held in conditions totally unsuited to meeting even their basic needs.
"People have a right to expect justice to be done, but many are living out their old age in conditions that demean both them and us.
"A just system tempers retribution with mercy, and we need to ask ourselves if we are getting that balance right.”
In a meeting with his Cabinet colleagues, Justice Secretary, David Lidington, said he was working to meet the challenge of an ageing prison population.
A Downing Street spokesman said: "The Justice Secretary said there are now a number of people in prison who are aged in their 90s. One factor behind this is the number of convictions
for historic sex offences.
"Having people in prison who are in their 80s or in their 90s - they have very specific needs in terms of their healthcare and you obviously need a prison system which is equipped to cope with those."
Source: The Telegraph