Diabetes sufferers who take the insulin product Mixtard 30 have been told they must switch to an alternative drug by the end of year, in a move widely criticised by health experts.
Pharmaceutical firm Novo Nordisk has decided to withdraw the medicine, which is taken by an estimated 90,000 diabetes patients in the UK.
A spokesman for the Department of Health has accused the company of ceasing its supply of Mixtard 30 for commercial reasons alone.
She said: "Patients on Mixtard 30 should continue to take it for the time being. Novo Nordisk's decision to withdraw the medicine is a commercial one and there are no safety concerns about this product.
"Healthcare professionals have been asked to set up appointments with those affected to discuss a suitable alternative treatment.
"Every patient will receive the very best care, support and monitoring during the transition period. This will be completed in time for the product's withdrawal at the end of the year."
Leading academics have also hit out at the decision in a letter in the Daily Telegraph.
The signatories - who include Jenny Hirst of the Insulin Dependent Diabetes Trust - said some patients would need many months to become established on different insulin treatments.
"Crucially, scientific evidence indicates that alternative forms of insulin promoted by the company, such as NovoMix 30, are neither more effective nor safer," they said.
"But they are much more expensive, with one estimate suggesting that a straight switch to NovoMix 30 for patients in England alone would add around £9m to the NHS drugs bill."
They added: "We are alarmed by Novo Nordisk's attitude to people with diabetes who rely on Mixtard 30, and we urge the company to reverse a decision that is not in the interest of patients, health-care professionals or the NHS."
Mixtard 30 - which is being discontinued from 31 December this year - is recommended by NICE.