Environment Agency surveyed the river, which is famous for its sea trout, last January after people living in Llandeilo noticed a white substance in the water.

The River Tywi is internationally renowned for its wildlife and is considered to be one of the finest sea trout fisheries in the whole of Europe

Peter Jordan, Environment Agency

The discharge was found to be sewage from the ACC Manufacturing Creamery in Llangadog and a month later further pollution was discovered during routine tests.

At a magistrates hearing at Ammanford on Monday the firm pleaded guilty to the offences and was ordered to pay �3,776 costs to Environment Agency Wales.

After the hearing Peter Jordan, environment protection team leader for the south west, said: "The River Tywi is internationally renowned for its wildlife and is considered to be one of the finest sea trout fisheries in the whole of Europe.

"It's importance brings economic benefits to south west Wales and some figures quoted suggest sums of several million pounds of benefits to the local economy every year.

"The fish and animals that make the river their home rely on excellent water quality and quantity, and incidents, which impact heavily on the environment, are deeply saddening."

Pump failure

During the investigations the agency also found the creamery had taken 7% more water out of the river than it was permitted to do.

The agency found significant amounts of sewage fungus in the river and growths were identified as far as 15 kilometres downstream from the discharge point.

The reports concluded that pump failure was to blame for the pollution.

Although most famous for its fishing, the River Tywi is also home to some rare fish species, including the twaite shads, small members of the herring family.

The shad spawn in only a few rivers in the UK, including the Wye and the Usk, but are becoming rare in rivers due to fishing, pollution and their inability to negotiate weirs.