Watercress and salads supplier Vitacress has spoken out after criticism of its environmental practices by a local activist.

Earlier this month William Daniel of Famous Fishing had complained to the Environment Agency (EA) in Hampshire about Portuguese sand that it had found in the man-made outflow ditch from Vitacress's plant at St Mary Bourne. He also suggested that the outflow from Vitacress's washing plant was affecting the population of invertebrates in the stream and calling on the agency to conduct an investigation and prosecute Vitacress. The criticism comes as Vitacress has been granted planning permission to expand its operations in the village.

The EA has confirmed that it is working closely with Vitacress. "We are discussing with Vitacress ways to minimise silt of a non-local nature,' said a spokesman for the EA. "We are working to ensure that it is trapped before it enters the outflow. Vitacress has consent to discharge to certain levels. We are making sure this is abided by and tightened up if the company is overlooking any aspect of it."

And Vitacress is standing by its environmental credentials. "We comply fully with all EA parameters," said Vitacress's Steve Rothwell. "We have spent many thousands of pounds to improve the quality of the 300 yards of fresh water in question."

Dr Rothwell acknowledged the "subtle invertebrate imbalance declining with distance" found by the EA in the channel and explained that the company has carried out research at its own expense, discovering that mustard oil which occurs naturally in watercress is toxic to invertebrates. "We have also spent £300,000 putting sediment traps in and have won a national environmental award," said Dr Rothwell. The company is trying to forge ahead with a managed wetland schemewhich has the backing of botanist David Bellamy but is being thwarted by the owner of local fishing rights who is advised by Mr Daniel.