However, the work has been questioned by the primary producers of atrazine, the Swiss-based agrochemical giant Syngenta.

BBC: Weedkiller 'threatens frogs'

One of the world's most commonly used herbicides, atrazine, poses a serious threat to frogs and other amphibians, American scientists claim.

BBC: Weedkiller 'threatens frogs'

"These studies clearly indicate that atrazine is detrimental to amphibians, " said Dr Tyrone Hayes, associate professor of integrative biology at the University of California at Berkeley.

BBC: Weedkiller 'threatens frogs'

It says the effects noted by Dr Hayes' team have long been observed in the wild - even before atrazine was marketed - and there is no established evidence to link the two.

BBC: Weedkiller 'threatens frogs'