Lethal litter and illegal bait diggers in Holes Bay are making a mockery of the designations heaped on one of the largest natural harbours in the world, it is claimed.

Poole Harbour is so crucial as a wildlife habitat that it is recognised internationally and the scenic lagoon enjoys the highest protections.

But concerns have been raised that the sensitive site is being neglected by those charged with its care.

Marine photographer and conservationist, Steve Trewhella, was stunned when he saw the rubbish accumulating in the inner harbour, right by the town centre.

“I was shocked by the huge amount of litter on the saltmarsh, many of the plants smothered in a layer of plastic and other rubbish – broken bottles, traffic cones and shopping trolleys,” he said.

However there is a suspicion that the precious environment is being further harmed by teams of illegal bait diggers.

Poole Harbour is a Site of Special Scientific Interest, marking it out as being among the country’s very best wildlife and geographical sites.

It is a Special Protection Area under the EC Birds Directive, classified for rare and vulnerable birds and for regularly occurring migratory species.

And it is notified as a Ramsar site, a wetland of international importance.

Thousands of wading birds feed in Holes Bay every winter including avocet and black tailed godwit, it hosts migrating and breeding birds along with many rare and uncommon plants and invertebrates.

Under a right granted as far back as Magna Carta, bait can be dug for anglers’ use – but it is illegal to dig it to sell commercially. And if large holes are left in mudflats they are not recolonised by worms for weeks, depriving birds of vital food.

“I worry that our promised Marine Reserves will be given the same useless unenforceable protection,” said Steve. “Giving species and habitats names is easy, but without enforcement they become a mockery.”

One of the problems appears to be that so many different bodies are involved in overseeing the harbour.

An aquatic management plan was worked up in 2006 through a steering group, composed of eight bodies, including local authorities, which all have statutory responsibilities in the harbour.

A bylaw proposed by Poole council in 2007/8 to control bait digging during the particularly sensitive times for birds of January and February, faltered on that very issue.

“We did try to get a bylaw to introduce some controls to bait digging in the harbour,” said Clive Smith, Poole council’s head of leisure services.

“Unfortunately the difficulties of getting all the agreements in place including all the land owners, prevented us from achieving this.”

The same is true with litter – above the high tide mark the responsibility falls to the council. In the water it’s Poole Harbour Commissioners.

Cllr Don Collier, Poole council’s cabinet portfolio holder for the environment, said cleansing service teams regularly cleaned above the high-tide mark, boosted by community litter picks.

“Irresponsible littering and fly-tipping presents potential dangers to wildlife and we would appeal to everyone to help by not littering and disposing of their waste responsibly,” he said.

Harbour master, Brian Murphy, said: “We have a joint agreement with Poole council where we help each other out. We do clean our own foreshores.”

He said it was hard to be certain that bait digging was commercial. And yet another body, Southern Sea Fisheries, was responsible for enforcement.

“Even though there’s a van and a team of men, it’s very difficult to prove. Unless we track it all back to a shop and money changes hands,” he added.

Natural England, the government’s adviser on the environment, said in a statement that it does have concerns about the level of bait digging in Holes Bay.

“The sheltered nature of the bay means that it can take a long time for the disturbed mud to weather down. It is therefore important that bait diggers back-fill their holes.”

It said: “There is also a concern that there may be toxic contaminants in the sediment and that very intensive bait digging may possibly raise toxins to upper sediment layers.

“Measures have been taken to reduce litter such as awareness-raising leaflets and waste facilities in marinas. A programme of regular beach cleans in the harbour will also be started shortly.”