Her website carries a statement that, due to illness, she is no longer available to speak or respond to emails.
The author of ''He'll Be OK - Growing Gorgeous Boys into Good Men'' and former manager of Christchurch Women's Prison was hospitalised after Christmas and a scan revealed pancreatic cancer.
In the statement, her family said her condition had deteriorated significantly in the last six weeks.
"Late last year I slowly became unwell. The stress of the lifestyle I was living, the demands I made of myself, the demands other people made of me and expected to meet became too great and as 2014 closed I was diagnosed with pancreatic cancer that had spread to my liver.
"No treatment, no cure, only palliative care. I'd waited too long to look after myself and my body broke," she wrote on her website.
"It's time to leave the work to others now."
She added: "I'm now focused on the moments of magic that are appearing in front of me: The laughter of my grandchildren; a smile of a friend attempting to walk this journey with me and the pure beauty and strength of my adult children as they battle their anger, grief and sadness at what is happening to their beloved mother."
Ms Lashlie's work on raising teenage boys as well as on social justice issues saw her in demand for speaking in New Zealand, Australia, South Africa and the United States.
Her statement today said: "Celia and her family hope that much of this work will continue through public support to honour her extensive contribution to social justice and her dream to improve the lives of at-risk families in order to reduce crime and poverty in this country."
She is best known for her work with the 'Good Man' project that focused on research from discussions with pupils in 25 boys' schools throughout the country.
It formed the basis of her book, He'll Be Ok. She has also written two other books -- The Journey to Prison: Who Goes and Why, and The Power of Mothers: Releasing Our Children.
Her advice to mothers of boys became well-known.
If adolescent boys could tell their mothers one thing, what would it be, she famously asked? Chill out and stop asking so many questions, was her answer.
Ms Lashlie worked for 15 years within the Prison Service from 1985. She was the first woman to work as a prison officer in a male prison in New Zealand.
Her website, perhaps summed up her later work with its motto: "Every child is born pure and filled with their own particular brand of magic."
She is the mother of two adult children and 'Nana' to five grandchildren.
Her family has asked for privacy as Celia has chosen to stay in her Wellington home surrounded by her family.
Lashlie was a New Zealand Herald New Zealander of the Year in 2001.
