Noel Edmonds has suggested that a cancer sufferer's ill health is caused by his "negative attitude".
The TV presenter is a user of the EMPpad, a machine which aims to stimulate "cellular resonance" in the body.
But he did not take kindly to criticism from @VaunEarl, whose Twitter biography states he has kidney cancer, lymph node metastases and psoriatic arthritis.
Edmonds quickly fired back that the Twitter user's ill health could be caused by "negative attitude".
Deal Or No Deal presenter Edmonds is a long-time fan of the device and has previously called it a "miracle pad", frequently recommending it to his followers.
He has said it can improve sleep, bring better health, reduce stress and even have an anti-ageing effect.
The TV presenter also claimed on Twitter that since he has started using the EMPpad he has been forced to cut his hair once a week.
EMPpad Limited said it does not pay Edmonds to advertise the product.
@VaunEarl's full name appears to be Vaun Earl Norman, and he also runs a blog titled My Adventures in Cancerland. Understandably, he seems less than impressed by allegations of a "negative attitude".
EMPpad Limited company director Maria Robertson has previously worked as an assistant to Edmonds.
In the acknowledgements section of his book Positively Happy, he wrote: "To Maria Robertson - heartfelt thanks and enduring gratitude for your support, commitment and love beyond the call of duty."