The chair and chief executive of a foundation trust have resigned ahead of the first regulatory report triggered by mortality figures.
The Healthcare Commission began its investigation at Mid Staffordshire foundation trust in March last year in response to several mortality rate alerts at the trust. Its report is expected this month.
Chief executive Martin Yeates and chair Toni Brisby left last week.
In a letter to the trust's governors the regulator Monitor said the findings were likely to highlight "inadequacies in aspects of the quality of clinical and nursing care… alongside broader governance and senior management failings".
It intervened to select replacement interim board members and said the trust was "already facing a crisis of public confidence".
Details of the Healthcare Commission's report are not yet known.
However, head of investigations Nigel Ellis said: "The organisation made an assumption that coding must have been the reason. What we would look for is the open minded response, which is to make sure there is not a problem with clinical care. In the main that is the response we are hearing."
Chesterfield Royal Hospital foundation trust chief executive Eric Morton has been appointed as interim chief executive and Sheffield Teaching Hospitals foundation trust chair David Stone has been given the interim chair role.