At least one in three heart surgeons has refused to treat critically ill patients because they are worried it will affect their mortality ratings if things go wrong.

Patients have been able to see league tables showing how well surgeons perform since 2014.

But consultant cardiac surgeon Samer Nashef warned that increased transparency had led to doctors gaming the system to avoid poor scores.

For his new book The Naked Surgeon, Dr Nashef anonymously polled heart surgeons asking them if they had ever boosted their ratings by refusing to operate on patients who they feared might die in theatre.

He said it "confirmed without any doubt" that clinical decision-making had been adversely affected by the culture of transparency.