It wants to reinstate wetlands which were drained to create extra farmland more than 200 years ago at the Tamar Valley near Cotehele.

Residents oppose the plan, which council leaders turned down in 2002.

The trust said there would be long-term gain because the area would become an important habitat for rare animals and plants if it was allowed to go ahead.

Important habitat

Under the proposals, a riverbank would be breached in three places to allow water on to about 35 acres of agricultural land to help form a reed bed.

At first, the area would be turned to mud by the flooding. The reed bed would appear over a period of between 10 and 20 years.

The National Trust said the area would become an important habitat for rare animals such as the water vole. The Trust said it also planned to put in a walkway to allow public access.

The National Trust project is vandalism Diana Greene

The trust wanted to flood the area three years ago but was turned down by Caradon District Council because of concerns about the effect on boats navigating the River Tamar.

Brian Muelaner, the trust's property manager for South East Cornwall, said: "We would like the natural processes to take place again and allow nature to recreate the inter-tidal wetland.

"This is one of the rarest habitats of its type on Earth."

But resident Diana Greene, who lives near the site, said: "This beautiful pasture, which is like something out of John Constable, is absolutely stunning.