The crisis of loneliness identified this week by Theresa May could get worse unless Britain’s charities start persuading more people who are poor, old, ill and from ethnic minorities to start volunteering, a government-funded study says.

The profile of Britain’s older population is set to change considerably in the coming decades to include more of those groups, but organisations that require volunteers have failed to attract them and have even sought to remove people who have developed physical or cognitive impairment, the study found.

Research suggests volunteering can help prevent loneliness and there is hard data to show it improves mental wellbeing and social connections, but rates of formal volunteering in the UK are significantly lower among black and minority ethnic people and poorer people.

Rates also drop off considerably when people pass the age of 75, even though the average life expectancy at birth is now 83 for women and 79 for men. Three times more people in the richest 20% of society volunteer formally than people in the poorest 20%.

“Lots of charities have been complacent,” said Dan Jones, a director at the Centre for Ageing Better, which produced the report with funding from the government’s Office of Civil Society. “It is not that they have been biased. It is just that when they needed more volunteers they asked Marjorie and Gladys to get some of their friends along and they were a lot like Marjorie and Gladys.”

Three-quarters of GPs have said they see between one and five people a day suffering from loneliness, and about 200,000 older people have not had a conversation with a friend or relative in more than a month, according to government figures. It is estimated that 4 million people aged over 65 volunteer formally or informally once a month – just over a third of that group.

Ethnic minorities tend to show higher levels of informal volunteering than white people, for example at mosques or community centres. But Jones voiced concerns that relying on that tendency would not encourage integration. The study found that 23% of white people volunteer formally, compared with 20% of black and minority ethnic people.

There is also evidence that the “white civic core” that charities have regarded as their workhorses are dropping out of volunteering, sometimes to look after elderly relatives or sometimes because they are becoming incapacitated.

“In future the older population will be more ethnically diverse and more people will live for longer with long-term conditions,” the report states. “These are precisely the groups who currently face the greatest barriers to getting involved.

“We found that people in later life experience significant emotional barriers to getting involved, which is not something that’s been reported for younger people. Fears of ageism, of being rejected or of ending up overcommitted, lack of confidence and a sense of not being welcome or valued can all stop people taking part.”

The Centre for Ageing Better plans to test methods of boosting involvement in five areas over the next six months. Grants worth a total of £500,000 will be made to charities that agree to try to bring in volunteers from marginalised groups and create models for lifelong contribution.

