Sussex is expected to lose one of its most popular tourist spots because environment managers say maintaining flood defences would be a waste of money.

Removing flood defences would abandon the Cuckmere Estuary, a beauty spot visited by 350,000 people a year, to the rising sea.

Homes which look on to the beautiful nature reserve, with its pretty meandering river, would be left in the middle of a muddy plain.

The Environment Agency said maintaining flood defences which protect the estuary near Seaford was not worth the millions of pounds it would cost.

Rupert Clubb, Sussex area manager for the Environment Agency, said it was not economically viable to try to stem the rising sea.

He said: "Over the next five, ten, 20 years there are certain areas we won't be defending.

"The Cuckmere Estuary and Medmery in Selsey are places where we shouldn't be investing millions of pounds for no return."

Sir John Harman, national chairman of the Environment Agency, said: "I think we are at the beginning of a long realisation that over the next ten years there must be a selective abandonment of agricultural land to create coastal marshes."

Sir John, who visited several sites in Sussex this week, said it was unlikely landowners in the UK would ever be compensated when their properties or land had been damaged by flood defences that were removed.

He said this was because it could encourage people to buy up land deliberately to receive compensation.

The agency sent out a consultation paper asking what local organisations thought it should do with the Cuckmere Estuary, near the Seven Sisters cliffs.

If waters are allowed in, the area would return to marshland. The Environment Agency argues this is a more natural state and would be beneficial to wildlife.

There are three properties which overlook the estuary.

None would be harmed by the removal of defences but they would find the countryside around them transformed.

One landowner has submitted his own planning application to bolster defences by an extra metre and delay the flooding for an estimated 50 years.

Nigel Newton, whose company Bloomsbury Books publishes the Harry Potter series, made the application as a protest against the agency's plans, which would leave his home in Coastguard Cottages, Cuckmere Haven, in the middle of a muddy plain.

Roger Frost, vice chairman of Seaford Residents' Association, said: "Personally I have opposed the idea right from the beginning.

"It is one of the biggest tourist attractions we have got in the area. They want to turn it into muddy flats."

Tony Rowswell, who has studied the plans on behalf of the residents' association, said: "The lower Cuckmere Valley is probably one of the most scenic views in Sussex. Everybody that goes along the A259 can see the meanders.

"We are destroying one of the most visible and beautiful pieces of landscape in Sussex. If you convert that into a tidal estuary it is going to be a sea of mud half the time."

The Golden Galleon pub in Exceat has views over the estuary. Sally Ellson, spokeswoman for Mitchells and Butlers Brewery, said: "We have got a great pub in a great location. It is an area of outstanding natural beauty and used by thousands of visitors.

"If the area was to change it could have an effect on our business. We are keen for it to remain as it is."

The Environment Agency is considering options including doing nothing and allowing the banks to break, allowing the western half to flood, or allowing flooding in the western half and part of the east.