Urgent government action has been demanded to prevent illegally-imported potatoes bringing a "grave risk" of pests and diseases into East Anglia.

Warnings were raised in a national farming magazine last month that 1,000 tonnes of "small ware" Agria potatoes have been imported as uncertified seed potatoes for spring planting in west Norfolk, south Lincolnshire and Cambridgeshire.

This would be a breach of biosecurity rules, following the post-Brexit ban on importing seed potatoes into the UK.

An East Anglian seed merchant, who did not wish to be identified, said there is a "grave risk of disease, and transmission of pests due to this lack of policing by our government body, Defra".

A government plant health spokesman said they would pursue "robust action" against any infringements as "the biosecurity risk of such practices cannot be overstated".

But the seed merchant said time was running out, as prosecuting people after the crops were planted was "similar to bolting the barn door after the horse has run away".

"The potatoes are imported in as 'small ware' under a passport system which does not identify the variety by name," they said.

"A month on from the discovery, nothing has been done whatsoever. Time is rapidly running away.

"The growers involved could end up being fined and these people should consider that they not only put themselves at great risk, but also others not involved in this heinous act.

"The rules are simple, the planting of ware potatoes or any other potatoes not obtained under any officially-approved programme or certification scheme are not legally allowed to be planted. If they are described as 'small ware' they are to be consumed for table or processing use only immediately or very shortly after they arrive in our area.

"Several ware and seed merchants in East Anglia and beyond are nervous and want Defra to react."

A spokesman for the Animal and Plant Health Agency (APHA), which is sponsored by Defra said: “We are aware of some operators attempting to circumvent plant health and marketing requirements following the ending of the temporary authorisation to market EU seed potatoes in Great Britain.

"These breaches are extremely serious and the biosecurity risk of such practices cannot be overstated.

“APHA will be pursuing robust action against any infringements and will be carrying out both general and targeted surveillance to ensure compliance – with enforcement action taken where offences are identified.”