An MP wants the collapse of two companies behind the Corran Resort and Spa in Laugharne, Carmarthenshire, to be looked into.
The hotel was bought by one of its directors after it went into administration with millions of pounds of debt.
MP Simon Hart told the BBC that the failed plan, which attracted £19m from 425 investors worldwide, should be examined.
Keith Stiles bought the hotel for £150,000 after an expansion plan he was involved in failed. The plan had involved building 200 eco lodges on marshland near the hotel, but planning permission was refused by Carmarthenshire council in 2015.
Owner Kayboo and operator East Marsh Operational went into administration in October 2016 and administrators sold the business to Glendore Real Estate, run by Stiles, in order to protect the 60-70 jobs there.
Hart told the BBC there were questions about whether investors knew there was a good chance planning permission may not be granted, as the site was on a floodplain and is a Site of Special Scientific Interest (SSSI).
"If the whole thing was sold, predicated on planning consent, there are big questions, because this was always going to be a big ask of the planners.
"I was in a meeting with [environment body] Natural Resources Wales and their arms were folded from the beginning," he said.
He has written to the UK government's Department for Business, Energy and Industrial Strategy asking it to look into what happened.
The directors of Kayboo and East Marsh Operational said the refusal of planning permission was unexpected and they would have met their financial obligations if their expansion plans had been passed.
They could not comment on Hart's calls for an investigation.
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