Paul O'Connor, chief executive of Birmingham Children's Hospital, resigned on Saturday with immediate effect, said its foundation trust chairwoman.

His resignation precedes the publication of a report by the Healthcare Commission, which investigated the hospital after concerns were raised by a number of its own doctors.

In a statement, Birmingham Children's Hospital NHS Foundation Trust chairwoman Joanna Davis said, "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."

According to an unpublished report that triggered the investigation doctors said they felt forced to lie to parents about why their child was undergoing a major operation, when in fact the hospital did not have the resources to carry out less risky procedures. Consultants said the hospital's treatment was worse than those offered in developing countries.

The Observer, a national newspaper said the report, commissioned by the NHS primary care trusts in Birmingham, found that support for surgeons undertaking kidney transplants at the hospital was poor. It reportedly found transplant services for children with serious liver failure were like "a third-class service" which was "putting patients at risk".

The report described "close calls" for children suffering neurological problems because of delays getting them admitted to the right specialist ward and said doctors had given up reporting safety risks because hospital managers failed to take action.

The report claimed that the staff who assisted in the complex surgery did not recognise which instruments were required, while services for rare conditions were "allowed to wither on the vine" because of a lack of investment. John Black, president of the Royal College of Surgeons of England, described its findings as "alarming".

After the contents of the initial report were made public the Prime Minister ordered the Healthcare Commission to investigate the matter. The Healthcare Commission probe was launched in November, and consultants across a range of specialisms were questioned.

The report is due within days in which they will assess the quality of services at the specialist hospital, which treats children for life-threatening conditions such as liver failure, neurological problems and heart complaints.

A Birmingham Children's Hospital spokeswoman said: "We can answer questions when the Healthcare Commission's report is out, but we cannot make any comments until that happens."