An American facing criminal charges after falsely claiming to cure cancer has been given glowing internet testimonials by the Glasgow doctor parents of singer Darius Campbell-Danesh.

Robert Young will appear in a California court today on 18 charges of theft and "treating the sick without a certificate" at his alternative retreat near San Diego.

Among other offences, the 63-year-old, who believes in the "pH Miracle" of avocado juice, is accused of taking more than $50,000 from a man dying of cancer, treating him without a licence and then asking staff at his centre not to tell the patient his disease had spread. The man subsequently died.

Mr Young, who made his name with best-selling books advocating a "pH diet", denies all the charges and insists he is the victim of persecution for his non-traditional beliefs. He has published a series of video testimonials from contented patients, including Mr Campbell-Danesh's parents, GP Avril Campbell and retired gastroenterologist Booth Danesh.

The accused, who refers to himself as Dr Young, citing a PhD from an alternative medicine college, tried to use the two ­Scottish doctors' credentials to support his treatments.

In his blog, he described Dr Campbell as a "world renowned specialist oncologist and research scientist". Dr Campbell herself, in her video testimonial, said she was an oncologist at Glasgow's Beatson West of Scotland Cancer Centre. She does work at the ­Beatson, as a speciality doctor, but is not officially registered with the General Medical Council as anything other than a GP.

NHS Greater Glasgow and Clyde yesterday distanced itself from the endorsement of Mr Young's brand, pH Miracle Living, with sources stressing that she was speaking in a purely personal capacity. A spokeswoman said: "The Beatson West of Scotland Cancer Centre has not heard of this product and in no way would endorse or support it."

Dr Campbell declined to comment when approached by The Herald. However, she sets out her support for Mr Young in three videos. She described how she was diagnosed with breast cancer and underwent "gruelling" chemotherapy and radiotherapy. She says she felt much better at Mr Young's centre on his trademark regimen of green foods, including avocado juice.

Watch the videos below

"I have no more pains," she said after 14 days on the treatment. She also said she now believed that she had a cancer in her thyroid, adding that a cyst discovered had seen a "measurable" reduction during her treatment. She added that she was going back to Scotland "to share my knowledge with colleagues and patients".

Dr Danesh featured in four videos, including one in which he is interviewed by an associate of Mr Young who describes him as "one of the most accomplished physicians and lecturers in Europe with a prominent role serving the Queen and Kingdom".

Dr Danesh, who has also survived cancer, retired from Stobhill Hospital a decade ago and is no longer licensed to practise medicine, according to his General Medical Council records. He said: "I wish Dr Young good luck". Both Dr Campbell and Dr Danesh filmed their videos about Mr Young and his methods in 2013, before the California practitioner was indicted early this year. Mr Young has a 1996 conviction for attempting to practise medicine without a licence.

Dr Campbell and Dr Danesh, who owns a firm offering medical services at his Bearsden address, are understood to have spent some weeks at Mr Young's retreat.

Mr Young has published a photograph on his blog of all three raising glasses of green liquid. The caption reads: "Dr Avril and Dr Booth have stated that Dr Young's research is revolutionary and should be taught to every medical doctor and integrated into every research, clinic and hospital around the world."

The American's books, including The pH Miracle and Reverse Cancer Now, have been widely condemned as pseudoscience.

Mr Young faces up to 15 years in jail if convicted. His indictment names six terminally ill patients who have all died. He charged one of them more than $120,000, according to detailed court papers.

His lawyer Paul Pfingst has previously said all the patients were aware that Mr Young was not a registered medical doctor. "People with a terminal illness can select how they want to be treated for the end of their days," the attorney said.

A Scottish cancer specialist contacted by The Herald said: "There is no way the Beatson will want to be associated with something like this."