Simon Hart MP is calling on the National Trust to take urgent action over mounds of rubbish and illegal camping taking place at a local beauty spot they own.
Mountains of waste have been left at Morfa Bychan near Pendine since the end of last summer and illegal campers have already pitched up this year.
"If this was happening at Freshwater West then quite rightly there would be a public outcry," said Mr Hart.
"Because this is a bit more hidden away there seems to be no urgency to clamp down on the problem."
The problem arises because a track that leads to the small cove means that anyone can drive down to the bay.
"Last summer there were people camping there for months and when they left there was a huge pile of waste – including a broken trampoline, kids' bikes and old mattresses," added Mr Hart. "It's been made worse because a plastic container that has also been left there is now being used like a skip and campers dump their black bin bags in it. These then get ripped open by gulls and the litter is blown up the valley.
"The rubbish was reported in September to Carmarthenshire County Council but no action has been taken yet.
"But this land is owned by the National Trust and I have written to them to ask that they urgently tidy it up and prevent fly camping.
"When I visited a few weeks' ago I was amazed to see four campervans and a caravan were there, they were clearly going to stay sometime as they had set up a pig roast."
Local resident Ruth Griffiths, who regularly walks down to the bay, said: "There have always been a few people camping down there on and off over the summer and no one minded as long as they left nothing behind, but now they turn up in campervans and stay for months and then leave so much rubbish behind. It is absolutely horrendous."
The road down to the bay is used regularly by Welsh Water as they need access to a reservoir pumping station in the bay and the lane is classified as a Byway Open to All Traffic (BOAT).
Mr Hart added: "As I understand it, this means that it is difficult to restrict vehicle access but I have asked the Trust to erect some "no camping" signs and for them to police the ban.
"This was one of the most beautiful and unspoilt bays in south west Wales and what is happening down there is a terrible shame."
Simon Hart MP
House of Commons
15, St John St
or 0207 219 3000