US developers’ controversial plans for a championship golf course at one of Scotland’s most prized wildlife sites are riddled with “embarrassing” flaws, including the claim that English law, rather than Scottish, governs the application.

Documents lodged with Highland Council in support of the development at Coul Links on the Sutherland coast mention birds that are not there, omit rare plants that are there and repeatedly, mistakenly, refer to English laws and agencies instead of those that cover Scotland.

Conservation groups argue that the multiple mistakes undermine the credibility of the planning application. But the developers defend their work, accusing critics of being “misleading and biased”.

The development is being proposed by Mike Keiser, a US property millionaire who has rivalled Donald Trump in the golf business. He has teamed up with a US banker and entrepreneur, Todd Warnock, who already owns property in nearby Dornoch.

They have submitted a planning application for an 18-hole golf course at Coul Links near the village of Embo. But the site is legally protected by three national and international nature conservation designations because its network of sand dunes is treasured for rare birds, plants and insects.

According to the Royal Society for the Protection of Birds (RSPB) in Scotland the application contains a series of mistakes. One document suggests that birds such as nightjars and Dartford warblers are at Coul Links when they are not, the society says.

RSPB points out that the environment management plan frequently refers to the Environment Agency, which covers England, instead of the Scottish Environment Protection Agency. In some documents figures and appendices are said not to match up and in one editorial questions remain in the text in red.

“RSPB Scotland has reviewed hundreds of environmental statements and this is certainly one of the more worrying we’ve seen,” said the group’s head of planning, Aedán Smith.

“It is particularly disappointing and concerning that the developer has not taken more time to ensure their basic planning paperwork is in order and is free of errors. This raises serious questions as to whether the environmental damage might be even greater than they predict.”

Smith argued that the golf course would destroy a significant part of a globally-important wildlife area. He also accused the developers of “salami-slicing” the proposal by trying to “rush through” a separate application for a large reservoir to irrigate the course.

Dr Tom Dargie, a leading expert on sand dune ecology and chair of the local opposition group, Not Coul, has pointed out other alleged errors. At least a third of the habitat on the site has been wrongly classified as wet or dry, he said.

He also alleged that the developers had missed a nationally-scarce plant, Baltic Rush, and significantly underestimated the number of rare dune juniper bushes. He accused them of mixing up native Scots pine and imported lodgepole pine trees.

Dargie insisted he had never come across such a “weak” application in the UK. He called on the government’s wildlife agency, Scottish Natural Heritage (SNH), to check it, and suggested that its ecological assessment was “invalid”.

The Scottish Wildlife Trust accused the developers of being out of their depth. “Alongside the embarrassing cut and paste mistakes about Dartford warblers are more worrying omissions and biases,” said chief executive, Jonny Hughes.

“The environmental statement assumes that the impact on dune habitats will be confined to the exact footprint of the greens, tees, fairways and rough. This is wrong, as any glance at peer-reviewed science will confirm.”

In response to the criticisms, the developers issued a joint statement. “All documentation produced as part of the environmental impact assessment process has been undertaken by a range of leading independent, experienced and professional consultancies,” it said.

“As a result, the validity of work undertaken and reporting is assured. The ecological surveys were conducted by experienced ecologists following standard good practice guidance.”

Any limitations and assumptions were clearly stated, the developers added. Analysis by Dargie “has shown a misleading and biased interpretation of the ecological survey work”, they alleged.

They stressed that local communities had reacted very positively to the proposed development, with 153 of the 173 who filled out a questionnaire at public meetings last week saying they were in favour.

The developers promised that they would “offset” the 14 hectares of a site of special scientific interest affected by the golf course with 20 hectares of improved wildlife habitat. They were now awaiting the “impartial view” of SNH and other official agencies.