The LGBT charity, known for its radical stance on trans rights, suggested 'improvements' to one hospital's guidance, was listed as a 'contributor' to another and 'validated' a third.
It is currently providing 'support' to another trust as it formulates its policy on caring for transgender patients.
Many trusts cited Stonewall, along with the scandal-hit trans youth charity Mermaids, as reputable sources of information. Last night a source close to Health Secretary Steve Barclay said he was 'appalled' that some NHS managers were engaged in 'woke virtue-signalling' by using outside groups to advise on equality issues despite his previous guidance against doing so.
It comes even as Stonewall has seen dozens of public sector bodies, including the Department of Health and Social Care, quit its 'diversity champions' advisory scheme in recent years.
A source close to Mr Barclay said: 'The Health Secretary has been clear that equality issues in healthcare services should be dealt with by normal management processes rather than by bringing in external providers.
'He is appalled to hear some managers are failing to respond and will be discussing with officials what further steps to take. NHS trusts and other health bodies should be relentlessly focused on caring for all patients and cutting waiting lists, not wasting time and money on woke virtue-signalling.'
The Government has pledged to update rules on hospital accommodation to protect all patients' privacy and dignity, the Mail revealed on Saturday. This is because anyone who identifies as a woman, even part-time, can access female-only wards.
Women's Rights Network founder Heather Binning said: 'The guidelines use the language of gender ideology repeatedly, and explicitly note that activist organisations including Stonewall helped to write them. They are representing the law as Stonewall would like it to be, not how it is.' Tory MP Nick Fletcher said: 'It is unacceptable that the NHS continues to place the safety and privacy of women at risk because of ideological capture by a tiny but vocal lobbying group.'
Analysis by the Mail of NHS trusts' policies on trans patients and staff found that as many as 30 cited Stonewall.
The Dudley Group NHS Foundation Trust listed Stonewall alongside its HR and LGBTQ+ teams as 'contributors' to its guidelines, while guidance by University Hospitals Sussex NHS Foundation Trust thanks Stonewall 'for reviewing and suggesting improvements'. It also states: 'Stonewall have an excellent ... language guide available online.'
Asked by this newspaper if it had policy on transgender patient care, Sandwell and West Birmingham NHS Trust said: 'We are in the process of drafting one with support from our LGBT Staff Network and Stonewall.'
Stonewall is included in a list of 'stakeholders' who have reviewed the diversity and inclusion policy of North Cumbria Integrated Care NHS Foundation Trust.
A Stonewall spokesman said: 'As the UK's largest LGBTQ+ charity, it is appropriate that we work with a wide range of public bodies to help them understand and meet the needs of lesbian, gay, bi and trans people.'
Comment: This is how a pathological minority captures a nation.