Both fear the move could threaten protected species on the Norfolk coast.

McDonnell Caravans, which is owned by the the Holkham Estate, is carrying out an "improvement programme" under permitted development rules over the winter on the site at Holme, near Hunstanton.

But neighbours are worried the work, which involves laying concrete slabs ready for new caravans, poses a threat to protected natterjack toads which are found around the village.

Retired accountant Fred Hallsworth, 72, who lives on nearby Kirkgate, has natterjacks in his garden close to the caravan site, which has permission for 64 static mobile homes.

Fred Hallsworth, who lives near the site at Holme (Image: Chris Bishop)

"The issue here is on the one hand you've got Holkham promoting itself as a bastion of ecology and on the other hand they've got massive earth moving equipment on the site during the natterjack toad's hibernation season," he said.

"With luck, they may have been woken up and escaped. More likely, they will have been scraped up and put in a concrete crusher.

"They are trashing a site that's 40m from an SSSI, in the middle of the natterjack toad hibernation."

Dr Steve Feast, who lives next door to the site (Image: Chris Bishop)

Retired doctor Steve Feast, 64, who also lives on Kirkgate, said: "Holkham laud their environmental credentials, so we as local neighbours were surprised that they appear to have taken their eye off the ball and allowed such a development in an area of environmental sensitivity.

"What's surprised and upset us is that as far as we can tell this is land owned by the Holkham Estate and is being developed by McDonnell Caravans for them.

"Given their commitment to conservation and what now appears to be the destruction of a very sensitive........

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