The chief executive of Birmingham Children's Hospital foundation trust has resigned ahead of a Healthcare Commission report.
Paul O'Connor is leaving with immediate effect, chair Joanna Davis announced in a statement.
The regulator began an investigation in November after it emerged that clinicians at the hospital and neighbouring trusts had concerns about standards and management.
'Lack of confidence'
They claimed there was "poor and disorganised management processes and lack of confidence in managers at all levels", a failure to report incidents and a feeling their complaints had not been taken seriously.
Ms Davis said in a statement: "The trust can confirm that Paul O'Connor, chief executive, has tendered his resignation with immediate effect. He has not been removed from his position.
"Further statements will be released in due course. However, at this stage, we can make no further comment."
Mr O'Connor was previously chief executive at Barnet and Chase Farm trust, London, under a franchise agreement.