The government has slashed the price of bluetongue vaccine in a bid to shift millions of doses before it goes out of date.

In an unexpected move likely to frustrate livestock producers who paid full price, DEFRA insisted it had no choice but to discount all remaining stocks of bluetongue vaccine by 50% with immediate effect. The same discount will apply in Wales.

Some 7.5m doses in 100ml bottles are languishing on DEFRA shelves after the government underwrote the production of BTV-8 vaccine last year. Due to expire this summer, it will leave the department with a £3.3m bill if unsold.

In an effort to cut its losses, DEFRA considered selling stocks abroad before deciding to discount the vaccine on the domestic market in the hope that doing so will encourage producer uptake and reduce taxpayer liability.

Chief veterinary officer Nigel Gibbens said: “This is an added incentive for those farmers who have not yet vaccinated their animals, or who are looking to give their stock a booster during the summer.

“With midges already active, and the Met Office predicting a warmer summer than last year, conditions for the spread of bluetongue may be ideal. Livestock keepers should take this opportunity to buy their vaccine at a discounted price.”

Vaccine will now be sold to wholesalers at 22p/ml rather at 44p/ml. If the discount is passed down the supply chain, the end price can be expected to halve from about £86 to £43 for a 100ml bottle. But it remains to be seen whether this happens.

In any case, retrospective discounts will not be applied – a situation described by NFU livestock chairman Alistair Mackintosh as “hellishly frustrating” for farmers who had already paid full price.

Peter Morris, chief executive of the National Sheep Association, said it was impossible to condemn DEFRA which was in a difficult position and obliged to obtain best value for taxpayer’s money.

“Vaccine is better in animals than on shelves. But the government must not be seen to be rewarding those producers who didn’t bother to vaccinate at the expense of those who were responsible and reacted swiftly.”

Nicky Paull, president of the British Veterinary Association, said she fully sympathised with farmers who would be thinking they could have vaccinated livestock much more cheaply had they only waited to do so.

“There was a clear understanding by practising veterinary surgeons and therefore their farming clients that the cost of bluetongue vaccine was likely to rise once the vaccine came under full market conditions.”

Rather than bad planning, DEFRA blamed the stockpile on a reduced appetite to vaccinate among farmers. “Vaccination is voluntary, and reduced uptake in 2009 has meant the government remains with unused stocks,” it said.