Marlborough town councillors have thrown their weight behind a campaign to stop Thames Water taking water out of the River Kennet to serve households in Swindon.
Campaigners say the removal of water is having a serious impact on the flora and fauna of the river.
At the town council's planning meeting on Monday, councillors read a letter from Action for the River Kennet, the local action group that is fighting to keep the river healthy.
ARK is particularly angry that Thames Water has waited until nearly the end of its ten year licence to apply for renewal from the Environment Agency.
ARK secretary Charlotte Hitchmough, said: "Thames Water has known for ten years the licence was due to come up for renewal but has waited until the last hour to reapply."
The group is now asking the Environment Agency to turn down the application.
Ms Hitchmough said: "There are plenty of places Thames Water could take their water from without harming the River Kennet.
"We are particularly concerned about the river flow at Axford. If it is too slow, silt in the water can settle and smother water plants, like water crowfoot, which fish and insects use to hide in.
"The river will cease to be a clear chalk stream and become a slow, brown trickle in which nothing can live."
Coun Peggy Dow said: "For years we have been muttering they have been taking too much water from the river, and now it is time to do something about it."
A Thames Water spokesman said the company is trying to reduce abstraction, but this would not be possible until a method of maintaining supplies had been put in place.
"This will be determined as part of a process of putting together our water resource plan. The draft plan will go out for consultation in April 2008," he said.
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