John Alexander, 72, has lived in Shoreham for 45 years and has been a regular visitor to Kingston Beach in that time.
The retired chartered engineer said the stretch of land near Shoreham Port has deteriorated to such an extent that it is now in the worst state he has ever seen.
“The little kids love to run on there and jump in the sea and it’s always been a safe place for people to swim around there,” said John.
“Now the only bit of concrete they have got to walk on has got more holes than a piece of Swiss cheese and it’s covered in sharp edges.”
John had been taking his 10-year-old granddaughter to play on the beach since she was a baby and said he used to be able to point out small areas of the beach that she should avoid.
The damage is now so widespread, he said, they have had to avoid the beach altogether.
“There are potholes the size of kids’ feet,” he said. “I would have no desire for my granddaughter to go anywhere near it, or anyone else’s kids.”
John said he believes the issues come from concrete built up over decades, which has been eroded and softened by the sea until it collapses, revealing pieces of jagged metal beneath.
The maintenance of part of Kingston Beach falls under the remit of Adur District Council, with the rest thought to be the responsibility of Shoreham Port.
A spokesman for Adur District Council said: “We are responsible for a small section of Kingston Beach and regularly carry out inspections to make sure the area is safe for all.
“No issues were apparent on our last visit and we have not had any concerns raised to us directly since then.”
Shoreham Port was approached for comment.