GWENT Wildlife Trust says the proposed M4 relief road would "wreak havoc" on one of the best wetland sites in South Wales.

To highlight its opposition to the new stretch of motorway, the Trust is holding a special event at its Magor Marsh reserve today on the Gwent Levels.

"Marshes or Motorway" will start with a guided tour of the site of special scientific interest (SSSI) and the public will be able to discuss the issues with people who live and work on the levels.

Trust chief executive Julian Branscombe said five miles of wetland would be directly affected by "this monstrous road proposal".

He explained Wales was fortunate to have some places left where rare aquatic flora and fauna survive.

"The Gwent Levels is a prime example. This is Wales' finest landscape, and includes two of Gwent Wildlife Trust's nature reserves - Magor Marsh and Solutia Meadows."

Mr Branscombe said water voles, the fastest-declining mammals, had been found there, while rare plants and insects could also be seen.

"Given this wealth of wetland wildlife, it is nothing short of criminal to see plans by the Welsh Assembly Government to drive a motorway through this precious resource."