Northamptonshire has become the latest county to be marked as a bluetongue restricted zone with over 150 farms now recording the disease.

After more cases were identified, the authority made the decision to add Northamptonshire to the list of restricted zones, which now encompasses 19 counties and one city authority in England.

The zone now covers all of Northamptonshire, Bedfordshire Buckinghamshire, Cambridgeshire, City of Kingston upon Hull, East Riding of Yorkshire and East Sussex.

It also covers Essex, Greater London, Hertfordshire, Kent, Lincolnshire, Norfolk, Nottinghamshire, Suffolk, Surrey and West Sussex, and parts of Hampshire, Berkshire and Leicestershire.

In its latest update Defra said: "Following the identification of a new case in cattle on the Buckinghamshire/Northamptonshire border, the restricted zone was extended on to include all of Northamptonshire."

Two cases of the disease have been confirmed in animals imported from England to Wales, but there are currently no restricted or control zones in Wales.

Farmers and livestock keepers in England's restricted zone must adhere to restrictions on the movement of animals and germinal products.

Susceptible animals cannot be moved out of the zone without a specific license, though a general license for moving animals to designated abattoirs is available. Movements within the restricted zone are allowed.

However, some farmers have raised concerns about price deductions being offered by abattoirs for animals from the bluetongue restriction zone.

The NFU said the development was 'unacceptable' and called for more fairness in the supply chain.

NFU livestock board chair, David Barton said: “We are incredibly disappointed to hear that some farmers in the restricted zone are being unfairly penalised by having deductions taken from some processors in the supply chain.

“Livestock farmers up and down the country are facing a very difficult time with the threat of the bluetongue virus and they are doing everything they can to limit the spread by adhering to biosecurity measures.

"We will continue to raise our concerns with Defra, that the requirements being imposed on processor is adding costs, but we must see farmers within the RZ are treated fairly.”

This comes after the government announced that all livestock keepers in England can use any of the approved bluetongue vaccines without needing to apply for a specific license.

But farmers must still comply with the legally binding conditions outlined in the general license for any vaccination activities.