A 'foreign object' was left inside a patient after an operation at the Norfolk and Norwich University Hospital, according to information released about the year 2011-2012.

It was one of four 'never events' – events which should never happen – at the hospital, the others being two incidents of wrong site surgery and one of a medication incident.

There were also 77 serious incidents at the hospital.

NHS Norfolk and Waveney as a whole has seen a large increase in serious incidents, from 117 in 2007-08, to 482 in 2011-12, with nine 'never events' in 2011-12, compared to none the year before.

However, NHS Norfolk and Waveney's board were told how this was mainly due to changes in the definition of reporting, which now requires pressure ulcers and more falls to be reported. Of the 482 serious incidents, 210 related to pressure ulcers and 52 to falls.

The East of England Ambulance Service had 15 serious incidents, the out-of-hours services had two, the mental health trust Norfolk and Suffolk Foundation Trust had 68, Norfolk prisons 16 and Norfolk Community Health and Care 133.

Chief executive Andrew Morgan questioned how worried the board should be about having even one 'never event'.

Maureen Carson, executive director of nursing, quality and patient safety, said: 'I don't think we would want any never event.

'The key issue is they aren't identifying trends. I think we should be working hard to ensure that numbers decrease, but I think we want them reported, we don't want them hidden, so we know that action is taken and they don't happen again.'

She told the meeting most of the pressure ulcers were being reported by community health staff, for a variety of reasons.

Dr Alistair Lipp , executive medical director, said: 'Never events reflect an aspiration and an expectation. They are not usually the result of an individual – it's a system or team failure.

'It often isn't a quick fix to mend because they require checking of policies and procedures, and then it takes time to bed-in any changes. One never event is a problem. Two similar never events is considerably worse.'