One million elderly people are chronically lonely, with many not seeing or even speaking to someone every day, charities have warned.
Almost a quarter of those aged over 75 who live alone go whole days without any human contact â€“ face-to-face or over the phone.
In total, one in ten men and women aged 65-plus â€“ equivalent to around 1million people â€“ are always or often lonely.
But, as the population ages, the problem will blight the lives of even more with 1.5million pensioners set to be affected by 2028.
Age UK and the Campaign to End Loneliness warn that social isolation can have a devastating impact on mental and physical health. ‘No one should have no one,’ they say.
The charities’ joint report details recent research which found that loneliness can be as bad for health as smoking 15 cigarettes a day.
Studies have also found that social isolation can be more damaging than not exercising â€“ and is twice as harmful as obesity.
Loneliness can also create deep mental scars, with research showing it increases the risk of depression and raises the odds of developing dementia by up to two-thirds.
Frailty, bereavement and fragmented families all compound the problem which the charities warn is becoming a major public health challenge.
The report also spells out the size of the problem. Almost half of all pensioners say their TV or their pet is their main source of company. Even those below retirement age are suffering from social isolation.
The charities say 13 per cent of those aged 55 and above only speak to another person three or four days a week. Although the proportion plagued by loneliness may not increase, the ageing population means the overall number could rise by 50 per cent before 2030.
Caroline Abrahams, Age UK’s charity director, said: ‘Loneliness is widespread among older people, leaving millions facing the ups and downs of later life largely alone. As the numbers of older people in our society increase, the problem is set to get even worse â€“ unless we do more to help older people avoid and overcome it.
‘Mounting evidence shows loneliness has a serious impact on our mental and physical health, which in turn can lead to greater reliance on health and social care services â€“ making it an issue we can ill-afford to ignore.’
Kevin Fenton, national director of health and wellbeing at Public Health England, said that for a growing number of older people, ‘loneliness defines and devastates their lives’.
The report evaluates the different schemes being used to tackle social isolation, adding that councils realise there is a problem but need more information on how to tackle it.
The importance of public transport is highlighted in the report.
Good access to transport is ‘vital’, not only to keep up with family and friends but to attend clubs and schemes designed to help pensioners meet other people.
Transport is a particular problem in rural areas, where just 61 per cent of residents live within 13 minutes of a regular bus service compared to 95 per cent of people in towns and cities.
Access to technology can also help stave off loneliness, with Skype video calls allowing people to see and speak to relatives or friends hundreds or even thousands of miles away at the click of a mouse.
One pensioner who is taking IT classes said: ‘I just click on and I can Skype Greece where my other family is. I can Skype them and see them, you know, it is out of this world.’
But, while more pensioners are becoming computer literate, almost five million people aged 65-plus have never used the internet.
The report, entitled Promising Approaches, says that while loneliness is a complex and time-consuming issue to tackle, the ‘devastating’ impact it has on those who suffer it every day mean it must be addressed.
The charities state that unless urgent action is taken, more older people will experience the ‘distressing daily grind’ of chronic loneliness.
Nearest tube: Elephant & Castle underground station (Northern and Bakerloo lines).
Nearest Railway Station: Elephant & Castle
Buses from Elephant and Castle: ask bus driver for Burgess Park. Bus numbers: 12, 171, 148, 176, 68, 484, 42, 40, 45