Claire Rayner, the doyenne of agony aunts whose warmth and wisdom imparted in her trademark gravelly tones made her the nation's favoured mother figure for four decades, has died after a long illness to which her family said she had typically refused to succumb.

With the sort of talent for no-nonsense and forthright statements that defined her life, Rayner, who was 79, told her relatives that she wanted the announcement of her death on Monday to be accompanied by her chosen last words: "Tell David Cameron that if he screws up my beloved NHS I'll come back and bloody haunt him."

Downing Street yesterday maintained a diplomatic silence on the former nurse's posthumous vow but warm praise came from across the spectrum of her many areas of activity and advocacy, ranging from the Patients' Association to the British Humanist Association to the Liberal Democrats, who she joined in 2001 after resigning in disgust from the Labour Party. In an article for The Independent, she said she could not agree with Tony Blair's health reforms.

The writer and broadcaster, who revealed late in her life that she had been mentally and physically abused as a child, devoted her life to caring for and representing others through her careers as a midwife, advice columnist and more latterly a campaigner on a bewildering array of issues. She was involved with more than 50 charities and was awarded an OBE in 1996 – an honour she openly admitted contradicted her lifelong republicanism.

After overcoming breast cancer at 70, Rayner had not recovered from emergency intestinal surgery in May this year and became progressively unwell. The eldest of her three children, Jay, food critic for The Observer, said she had stubbornly refused to surrender to her illness, undergoing dialysis on Sunday night, but died on Monday in hospital near her home in Harrow, north-west London.

Mr Rayner told BBC Radio 4's Today programme: "She would have always wanted to be the last person to leave the party and she was furious at going. She had led an absolutely amazing life and I am very, very proud of her. She was an agent provocateur. She liked to make mischief and infuriate people. I am assuming right now there are various columnists in the right-wing press who are sharpening their pencils to write about why Claire Rayner is responsible for the collapse of Western civilisation. I will be livid if they don't."

Indeed, such was Rayner's success in combining a matronly manner with progressive attitudes throughout the 1970s and 1980s that she was chosen to be first person to demonstrate on pre-watershed television how to put on a condom. She was also one of the first people to advertise sanitary towels on television.

In between raising her family and pursuing her journalistic career, Rayner found time to write nearly 100 books, including a succession of family saga novels which she said brought her significantly more income than her other lines of work.

But she will be most remembered for her work as a dispenser of unfussy truths on matters sexual, emotional and physical through the agony aunt columns of publications including The Sun, the Sunday Mirror and Woman's Own, and from her regular spot on the sofas of television programmes such as Pebble Mill, TV-am and Good Morning With Anne and Nick.

Asked to describe her work, Rayner once said: "I am the equivalent of the old girl who leans on her fence at the end of her village and says, 'Here, guess what I found out, and it might be useful to you'."

Tributes remarked on the energy and inspirational qualities the campaigner brought to her work, particularly as the president of the Patients' Association for almost 30 years.

Her close friend Baroness Helena Kennedy said: "She was an extraordinary woman – passionate, committed, warm and exuberant... Claire was a campaigner to her toes; her mission was to improve the lot of others."

Rayner's husband of 53 years, Des, who was also her agent and manager, said she had continued to be consulted by politicians and medical professionals on the provision of health services until her death. He said: "I am immensely proud of her. Through her work she helped hundreds of thousands of people and doubtless, by talking frankly about the importance of safe sex in the 80s when almost nobody else would discuss it, helped to save thousands of lives."

Born into an impoverished Jewish family in London's East End in 1931, she revealed in her 2003 autobiography that she had been beaten and effectively abandoned to the psychiatric ward of a hospital in Canada after her parents emigrated in the 1940s. She cut off all contact with her parents at 19 and returned to Britain to start a new life.

Virginia Ironside, The Independent's agony aunt, said: "After such a ghastly childhood, you either sink or you make something of yourself. She represented a 'pull your socks up' school of thought... There can be no doubt: she was a towering figure in British life."

Wit and wisdom: 'I'd be sorry if they just called me an agony aunt'

On marriage, sex and her childhood

"I'd grown up, I'd developed some self-esteem. And that made all the difference. And then dear old sex raised its ugly head of course. The first 20 years of my life were grotty in the extreme, and the rest were absolutely bliss. I've no complaints to make, 50 good years against 20 bad, it's a fair deal."

On having a double mastectomy in 2002 after being diagnosed with breast cancer, an issue on which she later campaigned

"I am fond of the old things, I've had them a long time. But I'm not defined by them."

On her need for two hearing aids in old age

"Why should hearing difficulties be shameful? You don't get it from sex; you don't get it from alcohol; you don't get it from being a nasty person. If you are deaf, you're deaf!"

On Pope Benedict XVI

"I have no language with which to adequately describe Joseph Alois Ratzinger, AKA the Pope. In all my years as a campaigner I have never felt such animus against any individual as I do against this creature. His views are so disgusting, so repellent and so hugely disgusting to the rest of us, that the only thing to do is to get rid of him."

On being Britain's best-known agony aunt

"I would be sorry if they just called me an agony aunt. There was a bit more on my plate than that.

It's like saying 'she ate potatoes'."

On tearing up her Labour Party membership in an article for 'The Independent' in 2001

"There is also their attitudes on fees for university students, provision for one-parent families and the disabled – it all shows that Labour has gone so far to the right it's out of sight. Principle has been sacrificed to power. Because I have stayed in the same place, they've betrayed me, and many voters like me. If all the people who are equally disenchanted with Labour moved to the Lib Dems, then Labour would get what it needs very badly. A powerful opposition. As for me, I still grieve. Fifty years is a long time."

On meeting her husband, Des, an actor, in the Fifties