Aldeburgh could eventually become an island if repairs are not made to its crumbling sea defences, a report by engineers Halcrow claims.
The Suffolk town could be cut adrift as money due to be spent on keeping out the sea will now go elsewhere after a change in funding priorities.
On Radio 4's Today programme John Gummer, MP for Suffolk Coastal, spoke of his fears for Aldeburgh.
Under threat are homes, coastal communities and Martello forts.
Thinly populated
The government is changing its priorities over which stretches to defend.
East Lane Point, south of Aldeburgh, has been identified as not worth defending because the area is too thinly populated.
Mr Gummer said: "If we change the way the coastline works there is the possibility of Aldeburgh being isolated.
"The Suffolk coastline could alter as far south as Felixstowe.
"The whole of the coastline is under threat. If a particular point is allowed to disappear beneath the sea, we not only lose a Martello Tower and a series of houses, we also change the way the coastline works," he added.
Pointing system
The Halcrow report identifies a crumbling WWII coastal battery as a key defence against erosion.
"If this should disappear Shingle Street could disappear in 20 years, the River Ore would silt up and lives as far inland as Hollesley could be threatened," says the report.
In response the Environment Agency said the government's pointing system does have implications for more rural areas where there are less properties at risk.
While accepting the need for repairs Steve Hayman, from the Environment Agency's Anglian Region, said:
"We obviously need to accept that is not feasible to protect the whole of the coastline."