Regency Land Sales and Regency Land Group – based in London, Spain and Belize – were found to have sold worthless land.
The companies – which have been wound up the High Court - attempted to sell land they did not own.
It comes after the IS warned last month that landbanking cons had doubled over the past two years.
The investigation found Regency Land Group used telesales methods to sell small plots of agricultural land in Grantham while Regency Land Sales acted as the UK sales agent for its offshore links.
The company insisted the land would increase in value when it was rezoned for planning purposes.
However, enquiries by The Government’s Companies Investigations, part of the IS, found there was no prospect of rezoning taking place.
And the IS complained Regency companies boss Llewellyn Adam Hannah-Smith and his colleagues failed to cooperate and provide full information during the investigation.
Investigators established the land sold was never legally transferred and purchasers were given a false guarantee of eight per cent growth on their investment in the first 12 months.
The probe found there was a lack of transparency about the management and status of Regency Land Group as a Belize-registered company.
Company bosses also admitted using aliases when talking to clients, as well as virtual offices and internet-based mail scanning services.
An IS spokesman said: "It was clear these companies were set up as an enormous confidence trick and members of the public were invited to invest on the basis of promised returns that were, at best, improbable.
"The IS will always take action to stamp out such practices in order to protect the general public."
Hannah-Shelton, who lives in Spain, also managed Britannia Land Management which was closed last month in the public interest, following similar concerns over its landbanking activities.
Last month, statistics released by the IS revealed that landbanking scams had gone up from 15 in 2009 to 30 this year.
Company investigations, which is the part of the IS tasked with tackling poor company practice, said that, since March 2007, it had wound up 50 landbanking companies.
It is estimated that losses from all landbanking scams now exceed £200 million.
By Andy Pearce