Almost half of night time emergency hospital operations involve junior staff, according to new research.

Concern was raised on Friday over the number of operations that involve patients being anaesthetised by a trainee doctor.

A report by the National Confidential Enquiry into Perioperative Deaths concluded that though there had been improvements over the last seven years more had to be done.

It also raised concerns over the lack of consultants working outside normal hours leaving junior surgeons to carry out procedures in 20 per cent of cases.

Dr Anthony Gray, lead clinical co-ordinator of NCEPOD, warned more action was needed.

"While it must be understood that many patients who require emergency operations at night are likely to be very sick, we still have the situation that in almost half the cases they will be anaesthetised, and in a fifth of cases operated on, by relatively inexperienced doctors," he said.

Officials at the Department of Health highlighted the report's positive findings, including a 50 per cent rise in the number of emergency operations over the last five years.

That was due to 3,300 more emergency operations being carried out in normal working hours when more staff were on duty.

"This reflects the hard work and commitment of NHS staff, who are increasing in numbers," said health minister Lord Warner.

He accepted the report's criticisms and pledged action.

"There are still too many emergency operations involving junior grades of medical staff without the supervision of a consultant and we will continue to invest more resources, work with staff and review working patterns to make sure that further progress is made," the minister said.