The publisher of a recipe book has admitted to never fact-checking claims made by the author that she survived terminal brain cancer through shunning conventional medical treatment, despite her story being used to market the book.

Belle Gibson launched a recipe and lifestyle app called The Whole Pantry off the back of her story that she had treated her terminal brain cancer through diet and lifestyle alone.

Last year she also launched her debut book in Australia, which is soon to be released overseas and contains recipes and lifestyle tips.

Her story of “treating” cancer without conventional medical treatment was used to market the book, which describes how Gibson “began a journey of self-education that resulted in her getting back to basics, as she set out to heal herself through nutrition and lifestyle changes”.

A spokesperson for the publisher told the Daily Mail that no proof of her illnesses was sought prior to publishing.

“We did not feel this was necessary as The Whole Pantry is a collection of food recipes, which Penguin has published in good faith,” she said.

“We are concerned about the questions raised in recent days – we’ll discuss them with Belle as ultimately only she can answer the questions.”

On Wednesday a Penguin spokeswoman told Guardian Australia: “We have no further comment to make at this time.”

This week, questions were raised about thousands of dollars in charity donations promised by Gibson off the back of money raised through the book and app, with The Whole Pantry admitting this week it had “cashflow problems,” and that the donations were never made.

But doubt has also been cast over Gibson’s cancer claims.

Gibson last year said she had been diagnosed with cancers of the liver, kidney, uterus, spleen and blood.

But she admitted in an interview with the Australian that those cancers may have been misdiagnosed by a German magnetic therapy “doctor”, who she refused to name.

Gibson maintains her diagnosis of brain cancer was accurate, but posts about her multiple heart surgeries, seizures and other cancers have been deleted over the past week, along with her social media accounts.

A former friend of Gibson’s told Guardian Australia that she had distanced herself from her after realising there was “something off” about her health claims.

“She was really into everything anti-medicine, including the anti-vaccination movement,” she said.

“She was very vague about her history and claimed she was estranged from both of her parents.

“I distanced myself from her after realising something was a bit off. She also lied to me about her age and claimed to be much older than she is.

“She has such influence, with 300,000 downloads of her app and people giving up their medical treatments to follow what she does, and it just didn’t sit right with me.”

The Australian reported that despite claiming to have been diagnosed with cancer in 1999 at age 20, Australian Securities & Investments Commission records show Gibson was born in October 1991.

The Whole Pantry app sells for $3.79, and is being developed as one of the first apps for the Apple Watch.

The Whole Pantry has been deleting angry comments left on their social media page by people angered by what they say may have been false claims by Gibson.

“Belle has multiple times promoted a ‘minimalist’ lifestyle, attacking consumerism lifestyles yet regularly posts photos of herself in exotic, not to mention expensive, destinations, first class flights – all of which are completely unnecessary if she wants to say it is in the name of her ‘business’,” one person wrote.

“Your company is built on a model of lies and deceiving people who have purchased a product based on a lie.”

Do you know more? melissa.davey@theguardian.com