More than 1,250 people have signed a petition started in the Black Country calling on the Government not to lift a ban on a “killer compost” which they say ruined their crops.

The on-line campaign, started by John Shobbrook of Black Horse Allotments Association in Wednesbury, has attracted signatures from all over the country and won support from a borough MP. Tom Watson, MP for West Bromwich East, today called for ministers at the Department for Environment, Food and Rural Affairs (Defra) to keep in force a ban on the herbicide called aminopyralid.

Last summer it was found to be contaminating manure and causing thousands of pounds worth of damage to crops and gardens.

It provoked an angry reaction from gardeners who saw many of their crops die or become stunted by the chemical. Mr Watson said: “I have seen lifelong gardeners and school children have their plots ruined by this chemical. We shouldn’t be risking it getting into the food chain again.

“It breaks my heart to see people’s efforts go to waste when this chemical, through no fault of their own, gets on to their land through a rogue supply of compost.”

Mr Shobbrook, aged 73, lost potatoes and runner beans last year after buying contaminated manure from a farmer in Aldridge.

He said: “The farmer would not have known the chemical was there. It can leak anywhere because it is a rogue substance.”

Aminopyralid is manufactured by Dow AgroSciences for control of broadleaf weeds on grassland, such as docks, thistles and nettles. It was first registered for use in 2005 in the USA.

It ends up on leaves and gets ingested by animals but poses no risk to them although it gets into their manure. After public pressure the Pesticides Safety Directorate, now the Chemical Regulations Directorate, suspended the sale of products containing aminopyralid whilst further investigations were undertaken last July.

Now a Government advisory committee has recommended that ministers should consider reinstating permission for the chemical whilst putting new safeguards in place. The petition is at www.petitions.number10.gov.uk