The medical adviser to the public inquiry into killings by the family doctor Harold Shipman has said he now believes that legalising assisted dying is necessary and would protect vulnerable patients. Aneez Esmail, a GP, was the only medical adviser to the inquiry in 2000 into Shipman’s mass murder of patients – killings facilitated by Shipman’s power as a GP. Esmail has written to all MPs this week urging them to back new legalisation on assisted dying for terminally ill people when the issue is voted on in the Commons next month. Shipman is believed to have killed about 260 patients, and many have pointed to his case as a reason to avoid legalising assisted death. While working on the Shipman inquiry, and for most of his career as a GP, Esmail was “implacably opposed” to doctors helping patients die and assisted in creating new rules that put clinicians under greater scrutiny. But he said that treating a dying man in extreme pain six years ago had changed his mind. Esmail now believes it is necessary to have the option to help those in the painful final days of terminal illnesses to die – and that greater regulation accompanying a change in the law would make it safer for patients. The emeritus professor of general practice at the University of Manchester told the Guardian: “The law is a mess and it doesn’t protect anyone.” He said palliative care doctors were already taking decisions to give higher doses of medicine to patients in acute pain at the end of life at a level that could hasten their death – but that it was not talked about. He said a change in the law would safeguard clinicians and patients in these situations and “make everything explicit” because “at the moment, it’s all hush, hush”. In his letter to MPs, Esmail wrote: “I have seen some people cite Harold Shipman as a reason why we should not legalise assisted dying. This is completely inappropriate and misguided. Power is a finite commodity. “Giving power to dying people means taking it from doctors and shifting further away from a paternalistic medical culture. Coupled with the greater regulation and oversight that an assisted dying law would bring, this would help prevent future situations involving bad actors within the medical system who have the means to carry out crimes.” Esmail’s letter came as the UK health secretary, Wes Streeting, said he would vote against the assisted dying bill, adding he had concluded that end-of-life care was not fit to deliver it safely. Speaking to Labour backbenchers, Streeting said he had initially believed in the right to choose by terminally ill patients but changed his mind given the degraded state of the health service. The health secretary’s comments are likely to seed some doubt among MPs before the free vote at the end of November. The justice secretary, Shabana Mahmood, has also said she will vote against the bill brought by the backbencher Kim Leadbeater, citing her faith as a reason to oppose it. Mahmood told the Times that she had an “unshakeable belief in the sanctity and the value of human life”. Keir Starmer, whose mother suffered from a degenerative illness, has said he is in favour of assisted dying and had promised there would be a parliamentary vote – though said it should come via a private members’ bill. Esmail said that until six years ago he “was implacably opposed to assisted dying as a doctor, because I believed, in my experience, that it was still possible to provide most people with good palliative care and they wouldn’t suffer.” He said that in around 2018 he treated a patient with mouth cancer “which was transformative” of his views on the issue. Esmail said of the patient: “He had this horrible ulcerating, fungating lesion in his mouth. His stomach was swollen. He could barely swallow anything. His breathing was being compromised. He was writhing in pain. “We were giving him morphine to an infusion pump, and it wasn’t making a difference … He was basically pleading with us, ‘Just let me die. Let me die.’ Short of me breaking the law and giving him a massive injection of morphine, there was nothing we could do.” Esmail became a trustee of the campaign group Dignity in Dying after changing his mind on the issue. He said that after Shipman’s convictions, doctors balancing the alleviation of extreme pain in terminally ill patients with the risk of hastening their death, were vulnerable to prosecution for humane decisions they took. “I remember a doctor coming to get a job with me who’d been investigated by the General Medical Council because he’d been accused of hastening someone’s death” Esmail said, “and his argument to me when we talked about this at the interview was that, well, I was simply doing what I thought was best for the patient. So I think it puts us in very difficult positions as doctors.” A vote on the terminally ill adults (end of life) bill is expected to take place on 29 November.