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".
She said she was "inundated with letters" after she wrote about her feelings in a newspaper and w hen older people told her that they felt as though "my days are pointless and I'm a waste of space", it left her angry.
Rantzen told the Radio Times: "I would come home at the end of a busy day, put my key into my front door, and find myself in a dark, empty flat. Nobody to ask about my day. Nobody to make a cup of tea for. Nobody to sit on the sofa with to watch the latest reality show."
The ChildLine founder said: "Something must be done to assure our older population that they are valued. We must reach out to them, link them back into their communities, and convince them that older people are a resource, a national treasure.
"There must be no sell-by date, no moment when older people become rubbish to be discarded, thrown away.
"Loneliness is, according to the Department of Health, as dangerous physically as smoking or obesity. Mentally and emotionally, it is utterly destructive."
The Silver Line helpline is launching across the UK on Monday.