TV presenter Esther Rantzen has called on society to do more to value older people.
The broadcaster said she discovered what it was like to feel lonely when she moved into a flat following the death of her husband, documentary maker Desmond Wilcox, in 2000.
Rantzen, 73, who is launching a helpline for older people, The Silver Line, told the Radio Times that loneliness was "the most terrible poverty of all".
"Something must be done to assure our older population that they are valued," she said.
"We must reach out to them, link them back into their communities, and convince them that older people are a resource, a national treasure."
Five hundred UK business leaders were questioned for the YouGov poll, conducted as part of an experts' meeting on ageing at London's Royal Institution.
- 40% said people aged over 50 accounted for a quarter of their workforce
- Two-thirds maintained that over-50s made an important contribution to their business
- Up to 81% were concerned that skills would be lost when older workers retire
- 19% of employers saw maintaining an older workforce as a business priority
- 12% invested in any sort of targeted training for older staff
- 4% had designed workplaces to make them more suitable for older workers
Essential skills will be lost unless employers do more to preserve the "mental capital" of older workers, a leading Government adviser has warned.
Professor Tom Kirkwood, an expert on ageing, was responding to survey findings suggesting that few employers were bothering to maintain an older workforce.
"There is real value in retaining the rich skills and experience of older workers but few businesses have yet caught on to the real potential of this population," he said.