The number of "lonely" over 50-year-olds is set to hit two million within seven years, Age UK has warned.
The charity said that the growing population of older people means more of them are going to be lonely and isolated in the future.
The figures came as a separate report showed that thousands of roles in the adult social care sector were left unfilled.
Figures from the English Longitudinal Study of Ageing show that around 7.5 per cent of people in this age group often feel lonely.
The charity said older people were particularly likely to feel lonely if they had recently been bereaved or had a relationship break down.
The most recent ONS data suggests that 1.4m people in England in this age group were lonely, a figure which is predicted to rise to 1.9m by 2020/21 and two million by 2025/6.
The charity is calling for a test for new Government initiatives to test the impact that they are likely to have on loneliness, by measuring how they affect communities and how isolated people are.
"People aged 50 and over are more likely to be lonely if they do not have someone to open up to, are widowed, are in poor health, are unable to do the things they want, feel that they do not belong in their neighbourhood or live alone," the report said.
Age UK’s charity director, Caroline Abrahams, said: “Our population is ageing quite fast and so we’re heading towards having two million lonely over-50s in less than a decade, with serious knock on consequences for their physical and mental health, and therefore for the NHS, unless we take action now."
A Department for Digital, Culture, Media and Sport spokesperson said: "We have set up an £11 million fund to better connect people across the country and our soon-to-be launched loneliness strategy - the first of its kind in the world - will be a step to overcoming social isolation within society.
"We welcome research and analysis from organisations, as this helps to develop a better understanding of the impact of loneliness on individuals and communities."
A stretched social care system which sees older people visited for very short periods and does not leave time for carers to have a conversation with their clients has been blamed for leaving some vulnerable older people feeling more isolated.
A social care green paper due to be released later this year will set out the Government's plans to reform the care system for older people.
Separate research published on Monday by Skills for Care, a training charity, found that around 110,000 jobs in adult care in England are currently vacant, 22,000 more than a year ago.
The sector's turnover rate had also risen, with 30.7 per cent of staff, equivalent to 390,000 people, leaving or changing jobs in 2017-18.
A Department of Health and Social Care spokeswoman said: "We are working to ensure the system is able to meet the demands of our growing ageing population and will soon launch a recruitment campaign to further raise the profile of the sector."