Outlandish plans to redevelop the estuary to generate electricity, at a cost per MWh of almost double any comparable low carbon energy source, would fundamentally alter one of the UK's most important wetlands.

Alongside the RSPB, Lincolnshire Wildlife Trust (LWT), the Wildfowl and Wetlands Trust (WWT) and Wild Ken Hill Estate, we are urging government and developers to re-think this proposal to avoid catastrophic effects on nature and wildlife.

The Wash is the UK's most important estuary for wild birds, home to England's largest common seal colony, and an important fishery. A tidal barrage would fundamentally alter the nature of the intertidal habitats on which this wildlife depends.

Construction of a barrier across the mouth of The Wash would displace the flow of tidal water in and out of the estuary, raising concerns this could lead to greater - and more frequent – flooding, and cause significant coastal erosion. Similar projects, including a tidal barrier at Oosterschelde in the Netherlands, resulted in flooding further along the coast.

The plans are fronted by businessman James Sutcliffe, CEO of Centre Port Holdings Ltd. A deep-water port has also been included in the plans.

The shallow waters of the Wash would make a deep-water port difficult, if not impossible, to build, and would require intensive dredging to maintain. It is unclear what effect this might have on nearby ports in Boston and King's Lynn.

Rivers flowing into The Wash deposit large amounts of sediment into the shallow estuary, making it one of the least suitable sites for the development of tidal power. About twenty per cent of England's landmass is drained by rivers flowing into the estuary.

Nick Bruce-White, director of RSPB England, says: "It's absolutely necessary to look at where the UK sources its energy and how we produce more of it ourselves from renewable sources, but we have to make sure we're striking the right balance for nature.

"The Wash is one of the most complex coastal habitats for its hydrology and stunning range of wildlife. Spending millions of pounds on assessments and surveys is a waste of time and money that could be better spent on more workable, established solutions to generate green energy, such as wind and solar power.

"Based on the current evidence that demonstrates the destruction this would bring to The Wash, we consider this project a non-starter."

This is not the first time ambitious proposals for a tidal barrage have been put forward. A similar development along the River Severn was dismissed by a House of Commons Select Committee in 2013 as "prohibitively expensive". The development was later cancelled on economic grounds.

Power generated by the Severn Estuary Barrage would have required massive investment and public subsidies at a total cost of more than £30bn, and the same would likely be true for the Wash Barrage.

Dr James Robinson, Director of Conservation at the WWT, says: "Building a barrage wouldn't address the energy crisis as it would take years to construct. It would, however, cause permanent damage to one of the UK's most important wetland habitats with devastating effects on biodiversity at a time when we are facing a biodiversity crisis in the UK and worldwide.

"It would also destroy saltmarsh, a vital carbon store that helps combat climate. If the UK Government is truly committed to recovering nature it must oppose any plans for a barrage across the Wash."

Not only is the wide estuary of global importance for its wildlife, but also for the carbon contained in its tidal habitats, and an important part of the government's commitment to protecting 30 per cent of land and sea for nature by 2030 and reaching net zero carbon emissions.

Tammy Smalley, from Lincolnshire Wildlife Trust, says: "Having grown up and lived around The Wash all my life, I know just what a special place it is and the vital service it provides to communities.

"As a natural flood defence, a source of food, and a wild place to visit, it should be protected at all costs - not destroyed to generate obscenely expensive energy and increase the risk of flooding."

The Wash is one of the UK's most important estuaries for wild birds - at any one time in the winter, up to 400,000 birds depend upon it for survival. It's estimated millions more use the area to feed, rest and breed over the course of a year.

Eliot Lyne, our CEO, says: "With its vast exposed mudflats and warm, shallow waters full of invertebrates, The Wash is one of the UK's most important estuaries for wild birds and supports internationally important bird populations including redshank and knot.

"To ensure we play our part in tackling the global biodiversity crisis, it is our responsibility to safeguard this incredible landscape."

Dominic Buscall, Project Manager at Wild Ken Hill, says: "The idea for a Wash Barrier is a non-starter. We absolutely cannot afford to interfere with this unique and incredibly special ecosystem, especially in light of the Government's commitment to stabilise the decline of biodiversity by 2030.

"A Wash Barrier is also likely to be deeply, deeply unpopular with residents around The Wash. We derive a huge variety of benefits and pleasures from living on the seaside, and do not want to live next to an artificial saltwater pond, nor the significant amount of new infrastructure required to service it."