Pain UK was established with £5,000 from Napp Pharmaceuticals, the UK manufacturer of OxyContin

A health charity urging GPs to “carry on” prescribing opioids was set up with funding from a maker of the powerful drugs.

Pain UK also benefits from professional lobbying assistance via a group that advises the world’s top pharmaceutical companies. The charity does not declare either relationship on its website.

The Charity Commission began a review this weekend after The Sunday Times handed it a dossier of evidence. Experts said the newspaper had uncovered a “mind-boggling number of conflicts of interest”.

The disclosures follow the unveiling of regulations aimed at raising awareness of the dangers of opioids. Matt Hancock, the health secretary, is bringing in “cigarette-style” warnings on pill packs after a Sunday Times investigation exposed a surge in addiction, overdoses and deaths.

Pain UK,