Her press agent, Pat Lake-Smith, said the 50-year-old entertainer's second husband, Kenneth Ives, was by her side.
Ms Caine discharged herself from hospital on Friday to go home, but suffered a relapse.
Ms Lake-Smith said last night: "Her condition deteriorated rapidly following a reaction totreatment for lymphoma.
"She had great courage, warmth and wit. She was a remarkable, wise and special woman and one of showbusiness's most loved entertainers. She will be greatly missed."
Marti Caine joked about everything, even the cancer which eventually killed her. When her Harley Street doctor diagnosed a malignant lymphoma in October 1988, she said: "Does this mean I'm a lymphomaniac?"
Born Lynne Denise Shepherd, in Sheffield, her father died when she was seven and her mother turned to drugs and drink.
For 15 years she played the tough working men's club circuit, earning pounds 7 a night. In 1975 she won ATV's New Faces talent competition and found fame.
In 1986, she became the hostess of the relaunched New Faces television talent show.
When cancer struck she was determined to work for as long as possible. Two years after being told she was dying, she appeared in pantomime in Bath.
"Losing my hair didn't bother me, which was a surprise, although you feel incredibly cold. I used to sleep in a woolly hat, which isn't very conducive to a romantic relationship," she said.
Throughout her illness she never lost her wit and love of life and she became an example for hundreds of other women who wrote to her telling her of their own cancers.