Severn Barrage build cost could top £15bn

A proposed tidal barrage across the river Severn could cost more than £15bn to build in real terms, a report has warned.

If built the Severn Barrage would provide about 5% of the UK's annual electricity demand.

But a report commissioned by a coalition of environmental groups including the National Trust, the RSPB and the WWF, challenged the idea that tidal energy from the river would be provided at peak times and suggested that 5m tonnes of CO2 would be emitted during its construction, along with another 5m during the transportation of materials.

It also warned that the projected £15bn cost did not take into account the cost of land acquisition in the surrounding areas of Cardiff and Weston, nor the creation of new wildlife habitat to compensate for lost land.

Speaking to the Guardian, RSPB chief executive Graham Wynne said: "There are good reasons for trying to harness the energy potential of the Severn estuary. But the estuary is truly exceptional for its ecological value."