Prescribing an expensive form of insulin against NICE guidance is causing the NHS to waste tens of millions of pounds every year, it has been revealed.

A joint investigation by the British Medical Journal (BMJ) and Channel 4 News has shown that around £250 million extra has been spent on insulin since 2005, despite NICE recommending a cheaper alternative.

Investigators discovered that the drug industry’s increased promotion of more expensive analogue insulins - to treat type-2 diabetes - has led to the additional costs.

But NICE had previously advised health professionals to prescribe human insulin as the best treatment for people with diabetes. A recent health technology assessment stated that analogue insulins were not providing value for money.

In the summer the National Prescribing Centre distributed advice on 15 areas of medicines that could be scrutinised to save money for NHS organisations.

This advice focused on NICE’s guidance of targeting long-acting insulins, with doctors needing to carefully think about the underlying causes of poor blood sugar control before prescribing newer, more expensive insulins.

Analogue insulin can be up to five times more expensive as regular insulin in some markets, accounting for an estimated 80% of insulin use in the UK, 70% in the United States and 60% in Europe.

The published data suggests that analogues do not improve glucose control or safety in type-2 diabetes, even though they have marginal benefits in terms of convenience, less weight gain and a reduced risk of hypoglycaemia.

Dr Amanda Adler, a diabetes expert at the University of Oxford, said: “I would estimate that around 90 per cent of people with type-2 diabetes would probably do quite well on these human insulins compared with the long-acting insulin analogues.”