A planning application bid for a £2.5bn theme park proposal in Kent will continue to go ahead after it was called into question by rivals who said they needed to be withdrawn.

Merlin Entertainments – which run Thorpe Park, Alton Towers and Madame Tussauds – claimed new submissions for the London Resort, planned to be between Dartford and Gravesend, amounted to a "material change".

The company, the second largest tourist attraction operator in the world behind Disney, said they wanted to see the plans pulled entirely to allow members of the public, authorities and businesses to comment due to what it said were fundamental changes taking place.

It comes after London Resort Company Holdings (LRCH), the group behind the proposals dubbed Britain's answer to Disneyland, were granted a four-month extension to amend plans after the Swanscombe Marshes were granted protected status.

The Planning Inspectorate gave LRCH the extension to alter their plans in line with the newly approved Site of Special Scientific Interest (SSSI) status awarded by Natural England in March.

Merlin chief operating officer Matt Jowett wrote to inspectors saying the company was considering legal action claiming LRCH was taking the extension to alter parts of its plans unrelated to the SSSI status.

He said information now being submitted was not part of the original application and means it "may well have resulted in different responses from the public or other stakeholders".

Mr Jowett added this risked the planning process "has not been properly carried out" meaning it could be subject to a legal challenge.

A host of environmental groups, including the RSPB and Bugslife, also wrote to the Planning Inspectorate saying the documents set to be submitted were considerably different to the original application.

But the leading member of the Planning Inspectorate panel which will assess the application says they will consider whether new documents "amount to a material change as and when they are submitted".

In a letter published this week, Stuart Cowperthwaite said the new timetable in which LRCH said it would be redrafting 203 documents and submitting two new papers as a result of the SSSI – which were contested by critics – did not "constitute a material change" to the application.

He added: "The Examining Authority will also consider the need for further consultation and any implications for the pre-Examination and Examination periods as and when the applicant submits any updated or new documents."

The date of the first public meeting which will set out exactly what issues will be considered and the timetable is likely to be later than originally planned, Mr Cowperthwaite added.

He said the panel was "not yet in position to finalise the dates".

It was initially expected the meeting would be held between September 27 and October 18 with final documents from LRCH due to be submitted by September 3.

Mr Cowperthwaite said inspectors would confirm the date once they had "an opportunity to review the updated and new documents and relevant consultation responses as and when they are submitted".

He added it was unlikely to hold the meeting before October 18 with a decision not expected until at least September 17.

Speaking previously, LRCH boss Pierre-Yves Gerbeau said there were no plans for any "material change" to the application but admitted there would have to be amendments taking into account the new SSSI status.

In April, LRCH released new details of one of the park's areas with a dinosaur themed section including Europe's fastest rollercoaster.

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