"Demi has previously discussed her history of disordered eating, so I'm surprised that she's accepting money to promote a weight loss gimmick.
"Some teas like this contain senna which has laxative effects. For some people this may result in diarrhoea. For those that suffer from constipation, it's putting a bandaid over the problem rather than searching for the root cause.
The programme involves the regular consumption of a 'colon cleansing' tea containing senna leaf, an ingredient which acts as an irritant inside the colon, which may prompt abdominal cramping and diarrhoea.
"I completely disagree with celebrities promoting any product which contains senna. Demi's fans are predominantly body conscious young women, they look up to her, and to promote such a product is dangerous.
Irish health experts have criticised Demi Lovato for promoting a 'detox' tea brand containing the laxative senna leaf, and warned of the damage products like this can have on long-term health.
Ruth Hetherington, creator of Miss Fit Skinny Tea, an Irish product which does not contain senna leaf or other laxatives, said celebrities and influencers need to be more conscious when it comes to the types of products they promote.
"I've seen one Irish influencer promoting a tea product with senna, but for the most part I do find bloggers and influencers in Ireland to be responsible," she said.