As experienced surgeons leave, he says, the more junior ones lose their mentors and become increasingly "risk averse", only choosing to use the healthiest donated organs offered to them.
Issues in heart and lung transplantation were first outlined in 2024 in a report commissioned by the Conservative government. NHS England, which was tasked with implementing report recommendations, says it has worked to "improve outcomes for patients", but surgeons and campaigners believe progress has been slow.
According to Robbie Burns, a former executive director at NHS hospitals and transplant recipient, who now works as a patient representative:
"There's been a lack of focus and a lack of oversight at a national level."I think the improvement has been extremely marginal and nowhere near the level that we need to achieve our goal of being a world-leading transplant service."
Sir Magdi Yacoub, an internationally acclaimed surgeon who helped establish the UK's once-leading reputation, told File on 4 Investigates that the NHS's issues stem from a continued lack of investment and deprioritising of services.
"We need to have more people, more money, physical resources," he says. "We have all the expertise... but we have slipped back in applying it to [patients]."
Responsibility for transplant services will soon be transferred to the Department of Health and Social Care (DHSC), following the decision to abolish NHS England.
The minister for transplantation, Dr Zubir Ahmed - who also works as a transplant surgeon in Glasgow - initially agreed to be interviewed by the BBC. When the government's press team was informed, the offer was retracted.
Instead, in a statement, the DHSC said the government had inherited a broken NHS and it recognised "the systemic issues facing cardiothoracic transplantation and the impact this is having on patients waiting for a life-saving transplant, as well as their loved ones".
A Birmingham surgeon speaking on behalf of NHS Blood and Transplant (NHSBT), which looks after services prior to transplantation, said NHSBT was aware of the problems in the system. "We're already trying to do better," Mr Aaron Ranasinghe told File on Four Investigates. "We're already doing better in terms of numbers of transplants building year on year. But we need adequate funding to follow that to allow us to reach potential."
When contacted by the BBC, the UK's transplant centres said they were continuing to develop their services and always kept patient safety and outcomes as their number one priority.