The Archbishop of York has called on Health Secretary Jeremy Hunt to intervene over the controversial decision to suspend children's congenital heart surgery at Leeds General Infirmary (LGI).
The hospital, which is engulfed in a long-running row over the future of its children's heart services, is carrying out an internal review after data suggested a death rate twice the national average.
Doubts have been cast over the reliability of the mortality figures after it emerged they did not include scores of operations carried out by the unit.
Dr John Sentamu, who has backed campaigners in their battle to keep children's heart surgery in Leeds, visited the unit on Saturday in a "pilgrimage of prayer and trust".
Speaking at the hospital, the archbishop asked Mr Hunt to "speedily" conduct his own review into the unit, which was ordered after opposition to plans to stop surgery in Leeds.
Dr Sentamu told ITV News: "The data on which it was based to close these surgical procedures needs to be analysed fast and quick. If it turns out not to be accurate then somebody's got to come clean about it. They should carry out what the court has asked and what the Secretary of State has embarked on and do it speedily and quickly and without any bias at all. I'd ask the Secretary of State really to intervene and come in pretty fast."
Campaigners have criticised the suspension of surgery and its timing, which came 24 hours after a High Court judge ruled the decision-making process to close the children's unit was "legally flawed".
Sir Bruce Keogh, the medical director of NHS England, said on Friday the figures were among a "constellation of reasons" to suspend operations, as well "disturbing" calls he received from two whistleblowers.
Elspeth Brown, consultant cardiologist at Leeds Teaching Hospitals NHS Trust, claimed the mortality figures for Leeds were "incomplete", with more than a third of cases missing. Just 180 operations out of more than 300 in the unit were considered in the figures, she said.
A spokesman from NHS England said: "We agree with the trust's decision to launch this review. It is really important that this review is carried out in a sensible, effective and decisive way. For that to happen it needs to follow a proper and complete process. It cannot be conducted in the media. The data and other information that triggered this precautionary pause have raised questions but they have not provided answers. That is the job of the review. It is important that the review is allowed to do its work properly and reach a decisive conclusion on behalf of patients."