A former health minister has accused the NHS of closing ranks after the deaths in hospital of elderly patients from alleged overprescribed painkiller drugs.

Norman Lamb said the NHS and elements of Whitehall had refused to face up to "hard and uncomfortable facts".

The Liberal Democrat MP served as a health minister between 2012-15 during the coalition government. He was speaking to the BBC on the eve of the publication of a report into hundreds of deaths at Gosport War Memorial Hospital near Portsmouth in the 1990s.

The former bishop of Liverpool James Jones has spent the last four years chairing an independent panel which has been examining the deaths of elderly patients who were allegedly prescribed the painkiller diamorphine. Jones chaired the independent Hillsborough panel.

Dr Jane Barton, a local GP who cared for the some of the patients at Gosport, was found guilty in 2010 by the General Medical Council of "serious professional misconduct" after it concluded that she had prescribed potentially hazardous levels of drugs. Dr Barton was not struck off and she chose to retire after the findings.

Police examined 92 cases among the 833 death certificates signed by the GP. Dr Barton has previously denied wrongdoing and has maintained that she always acted in the interests of her patients.

In an interview with BBC Newsnight Norman Lamb spoke of his anger when department of health officials advised him in 2013 that a public enquiry should not be held after the publication of an official report into the deaths. The report by Professor Richard Baker of Leicester University found that opiate painkillers had "almost certainly shortened the lives of some patients". The Baker report was completed in 2003 but not published until ten years later once all the inquests had been completed.

Media playback is unsupported on your device Media caption "There's been a real systemic failure here," says former health minister Norman Lamb

Lamb told BBC Newsnight: "I just think it's horrific and there has been a real systemic failure here, a closing of ranks in my view and a sense that ordinary people just weren't being listened to at all, and an unwillingness by the NHS to face up to some really serious allegations about what happened in that hospital."

The former minister recalled his reaction when he was advised by department of health officials in 2013, in an email sent to him on holiday in France, that a public enquiry should not be held. He said: "I was incandescent about this so I immediately sensed that there might have been a conspiracy to cover this up whilst I was out of the country. To this day I dont know whether it was cock up or cover up but I was very clear in my mind that there must on no account be that statement made the next day."

Lamb said he persuaded ministerial colleagues to launch the enquiry. The findings will be published tomorrow.

A spokesperson for the Department of Health and Social Care said: "Norman Lamb, in his capacity as a Minister at the Department of Health at the time, was instrumental in the decision to set up a panel investigation into the tragic events at Gosport. The Government, along with local NHS organisations and authorities, will receive a copy of the report tomorrow and we expect the findings to be studied closely and carefully by all relevant parties."