An allotment-holder in the Black Country has launched a national campaign to ban a weedkiller which has been blamed for tainting compost and destroying crops.

Government experts launched an investigation into the effects of compost said to be contaminated with the herbicide aminopyralid last year and related products were withdrawn from sale.

But manufacturers have now applied to get it back on the shelves, sparking fears more devastation awaits for growers.

Wednesbury gardener John Shobbrook has now launched a petition to the Prime Minister to ban the substance, with more than 500 people signed up in less than a week.

Mr Shobbrook, chairman of the Black Horse Allotments Association and ex-chairman of the Sandwell Allotments Council, was among campaigners who raised fears over distribution of manures containing aminopyralid last year. It was claimed plots were devastated at the Black Horse Allotments in Wednesbury Old Park Road as well as other sites, including some maintained by school children.

The industrial strength weedkiller finds its way into manure when ingested through grass by livestock, but manufacturers say strict instructions on where it is safe to use affected compost had not been followed.

Authorisation for its supply and sale as a weedkiller was voluntarily withdrawn to allow further investigations, but a Government advisory body has now recommended authorisation is restored.

Mr Shobbrook, aged 73, said: “When the herbicide gets into manure it is still active so when it arrives on your garden if you put it on your plots it kills it, so last year there were massive failures of potatoes, peas, soft fruits and roses, right across the country.

“I only started the petition last week and there are already more than 500 signatures. There are a lot of people on board.”

The petition is available on-line at the petitions section of the website www.number10.gov.uk