A 92-year-old widow from South Africa who wants to spend the “end of her days” with her only child in Britain is facing enforced removal from the UK even though she has heart problems, loss of sight in one eye and no family in her native land.

Myrtle Cothill has been cared for by her only daughter, 66-year-old Mary Wills, in Poole, Dorset, since February 2014, but recently received letters from Capita advising her to make immediate plans to leave the country after her visa application was rejected by immigration authorities.

Capita is a private firm hired by the Home Office to get those who outstay their visa to comply with the immigration application rulings. Wills, who holds a British passport, says the enforcers “will have to kill her” before they deport her mother.

She has also received instructions from immigration enforcement officials advising her her mother needs to sign in at Bournemouth police station on the first Wednesday in January.

The former Tory MP Ann Widdecombe, who has taken up the case of the South African pensioner, says the decision is “heartless in the extreme”. She added: “On this occasion the rule book has proved a brutal master instead of a useful servant.”

Saira Grant, legal and policy director at the Joint Council for the Welfare of Immigrants, said Cothill was a casualty of 2012 changes in immigration laws.

The new adult dependent rules say migrants “must as a result of age, illness or disability, require long term personal care: that is help performing everyday tasks, eg washing, dressing and cooking”. This means the 92-year-old has to prove she is dying before she can stay with her daughter, says Grant.

Cothill has an enlarged heart, poor hearing and has lost the sight in one eye because of macular degeneration but neither her condition nor her advanced age is enough to secure her the comfort of life with her daughter.

A Home Office spokesman said Cothill’s application was rejected as her “condition was not deemed to be life-threatening” and that “suitable medical treatment” was available in her country of origin.

Wills, who lost her father when she was a small child, has vowed to fight deportation. “I came into this world fatherless. My mother worked her fingers to the bone to educate me and to build a life for me. Why can’t I take care of her in her old age, like she did for me when I was a child? She is not a threat to anyone. It is just wrong to separate us.”

Cothill said she was very hurt at theHome Office ruling. Not only was was she born under the British flag in 1924, but her father fought for the UK in the first world war and her brother fought for the country in the second world war. She is also financially independent with a pension of £300 a month.

Asked how she would feel if she is removed from the country, Cothill said: “I don’t want to go. I’ve got nobody there and I am not well enough to travel. I’m very upset. I’m very old. I’m 92. I want to live with my daughter for the end of my days.”

Cothill’s case has come after the Parliamentary and Health Service Ombudsman said too many lives were being “put on hold” by the Home Office. It upheld 69% of immigration complaints about the Home Office largely centring on delays and discretionary decision making.

At her wit’s end, Wills has organised a petition on Change.org to try to persuade the Home Office to show some compassion and change their mind. “My mother just cannot live on her own,” she said. “And emotionally, to her as well as for myself, it would really tear strips out of our heart and probably would kill my mother.”

In the petition, her barrister, Jan Doerfel, has called on the Home Office to review its decision, but also to urgently reinstate the rules that operated for the previous 40 years, which allowed elderly dependents to join British nationals or other settled persons if they could be accommodated and financially supported by their children or grandchildren without reliance on the public purse.

Wills says she could not have gone to South Africa to look after her mother partly because her husband, who is British also, has Parkinson’s disease, and because she is not legally entitled to live there.