A wildlife haven home to scores of rare species threatened by development plans for the UK's largest theme park has been granted special protected status.

Marshland on the Swanscombe Peninsula, where developers hope to build the £2.5bn London Resort, has today been designated as a Site of Special Scientific Interest (SSSI).

The status granted by Natural England – the government's environmental advisory group – means any future development plans must take into account the abundance and important wildlife in the area.

But a leading figure from the RSPB says it should "end any debate" about building the theme park dubbed the Britain's answer to Disneyland.

Emma Marsh, the charity's England Director, said: "This is unashamedly good news and we applaud this step by Natural England.

"Recognition as an SSSI should end any debate about developing a theme park here.

"The focus should immediately turn to how Swanscombe Marshes can be effectively managed and monitored so that the species and habitats continue to thrive with their newfound status."

Jamie Robins is from Buglife

The marshes have been dubbed a "valuable green space" by Natural England which highlighted the variety of wildlife and plants and the importance of the area to residents and visitors.

The 250 hectare site on the banks of the Thames between Gravesend and Dartford is home to an array of grassland, scrub, wetlands, grazing marsh and saltmarsh habitats.

Natural England said the combination of these means Swanscombe provides "ideal conditions for a unique variety of wildlife".

The SSSI does not prevent development proposals but it means future development will have to seriously take into consideration ways to protect the environment and the affected area to protect the landscape and wildlife within its boundaries.

Natural England said it recognised there was interest for "potential development opportunities" but that designation of the site was granted due to it being "nationally important" for wildlife.

The body added SSSI status mean it was "an important step towards ensuring that its environmental value is recognised and taken due account of in any future planning decisions".

London Resort Company Holdings (LRCH) has submitted its 25,000-page planning application which is now being considered by planning inspectors from the government's Planning Inspectorate.

The examination is expected to last between 12 and 18 months.

Interested parties, community groups and residents have been called by inspectors to submit their views on the plans which will be heard during a series of public hearings over the coming months.

The London Resort project has been deemed a nationally significant infrastructure project (NSIP) by the Planning Inspectorate and is estimated to provide 48,000 direct and supply chain jobs during construction with 17,000 jobs at the park by 2038.

But bosses will now have to set out highly detailed mitigation plans to protect the environment as a result of the SSSI status being awarded.

The company says the park will be sustainable and carbon neutral while designs are said to incorporate the green space, improve access to the river and "showcase natural features of the site" which will be incorporated into the plans.

LRCH has also said a "large proportion" of the landscape on the Peninsula will be undeveloped and enhanced.

The area is home to more than 1,700 invertebrate species, a quarter of the UK's water beetle species and more than 200 different species considered of "conservatation importance", Natural England says.

It is also one of only two locations where the critically endangered distinguished jumping spider is found in the UK.

There is a wide range of breeding birds including the marsh harrier and bearded tit as well as scarce plants threatened with extinction in the country.

James Seymour, Sussex & Kent Area Manager, Natural England, said: “The designation of Swanscombe Peninsula as an SSSI is great news for one of the richest known sites in England for invertebrates, ensuring essential refuge for many rare and threatened species that sadly are not able to thrive in the wider landscape.

“Right on the doorstep of some of our most densely populated towns and cities, this new SSSI will also offer wonderful opportunities for people to connect with nature via the England Coast Path.

"This area is living proof that some of our most important species can thrive hand in hand with businesses and transport infrastructure.

"Special places like this will form the vital backbone of a national nature recovery network."

The new Swanscombe Peninsula SSSI merges with the already designated Bakers Hole SSSI, which covered 6.9 hectares and was listed for its geological and archaeological features which help scientists understand the glacial periods in the earth's history.

The government has pledged to protect 30% of the UK's land by 2030 with more than 4,000sq km of land in England being designated to protect land, water and sea areas to protect plants and wildlife as part of its plans to help the environment.

A four-month period now launches where the SSSI designation can be objected or appealed against.

Buglife, the RSPB and Kent Wildlife Trust have all welcomed the decision announced this morning.

The organisations had joined forces to fight for greater environmental protection for the area and a letter signed by 77 senior figures from conservation groups and public bodies.

A petition to "Save Swanscombe Marshes" has been signed by more than 22,000 people.

Matt Shardlow, chief executive of Buglife, said: “We thank Natural England for doing the right thing by protecting one of the country’s most important wildlife sites.

"However, the Swanscombe Peninsula remains under threat and it is crucial that a precedent isn’t set by allowing a fun fair to be considered as more important than the wildlife that inspires wonder and sustains us.”

Richard Bloor, wilder towns manager at Kent Wildlife Trust said, “It is fantastic that Natural England has, today, recognised that the Swanscombe Peninsula as a SSSI.

"This wildlife-rich area is now formally seen as a nationally important site that protects flagship species such as the critically endangered distinguished jumping spider, and populations of many other animals and plants. Despite this the fight to save this haven for wildlife is only just beginning.

"We must ensure that the Swanscombe Peninsula, alongside other SSSIs, are fully protected from any further development, and bought into better condition as part of the Nature Recovery Network, ensuring that the UK becomes a less nature-depleted place whilst tackling the nature and climate crises.”

London Resort boss PY Gerbeau said: "The challenges presented by the site are not unusual for major brownfield reclamations. The project will of course continue, and this is just another issue to address in the long history of this project.

“Sustainability is a green thread throughout the London Resort proposals and we’re very proud of that.

“We have demonstrated, across thousands of pages within our application, our vision to deliver a net gain in biodiversity and our commitment to enhancing and managing habitats. An investment that runs into millions because we believe in sustainability and in our role as custodians of the environment.

“We have shown how we plan to transform a contaminated, former industrial site, through this exceptional, once in a lifetime opportunity. An opportunity which will bring thousands of jobs, generate substantial economic growth and boost tourism with the UK’s first, world class theme park resort.

“No one knows more about the land than us because we have been surveying and monitoring it since 2012.

"We are the ones who have found and identified every species. We have shared our reports and we are working closely with Natural England to identify the right ecological solutions to deliver this grand project.

“The London Resort looks forward to the examination, led by the Planning Inspectorate and the decision, of the Secretary of State.”

Head to our business page for all of the latest news about businesses in Kent

Read more: All the latest news from Dartford