NATIONAL Trust chiefs have come under fire after weedkiller sprayed from a helicopter drifted across Studland's busy public beach.

Three members of the public complained to environmental health officers that they suffered smarting eyes and sore throats following the incident.

Purbeck District Council's environmental health manager Roger Garwood said: "The spraying took place on one of the busiest days of the year in windy weather by a packed beach - you could not have had worse conditions to spray in."

The National Trust was spraying the herbicide Asulox, containing the chemical Asulam, to control bracken around the lakes between Ferry Road and Studland beach on Sunday morning.

Mr Garwood said: "Three people complained to us, each independently complaining of smarting eyes and sore throats and that is exactly what the US Department of Agriculture says this product can cause.

"Two people phoned back saying the symptoms went away as soon as they came."

Geoff Hann, head warden for the National Trust's Purbeck estate, said: "The chemical is not toxic in any way. We've had no problem with it otherwise we would not use it."

He explained the spraying needed to be carried out in July to control invasive bracken and allow heathland to regenerate.

Mike Davis of MD Air Services, which operated the helicopter, said: "We took all the precautions possible and put notices up. The pilot would not spray anywhere within 200 metres of people knowing how sensitive people can be. As soon as the pilot became aware the wind had got up he stopped the operation."