Tenants of the Prince of Wales’s private estate have been barred from buying the freehold of their homes by laws vetted by the prince, it has been claimed.

Parts of Charles’ Duchy of Cornwall estate – a portfolio of land, property and investments worth more than £1 billion – are exempt from two property laws which give families the right to purchase their homes outright.

The Guardian claims research it carried out into archive documents show the exemptions were passed after Charles was given prior sight of the legislation under an obscure parliamentary process.

But a Duchy of Cornwall spokesman said: “Any assertion that the Prince of Wales has blocked or unduly influenced legislation is incorrect.”

Retired oil executive Alan Davis, a tenant on the Isles of Scilly, which is part of the Duchy of Cornwall, told the newspaper he has been unable to buy the freehold of the bungalow he purchased in 1984.

He has been affected by an exemption in the 1993 Leasehold Reform, Housing and Urban Development Act, which excludes Dartmoor, large parts of which are owned by the Duchy, and the Isles of Scilly.

With less than 65 years left to run on his lease he is concerned for the future value of his home, telling the Guardian: “The problem comes when you want to sell it. If the lease is down to something like 30-odd years, people will just shy away from it.”

He added it was “absolute nonsense” he and other residents could not buy their homes outright from the duchy.

The Oval cricket ground and Dartmoor Prison are just some of the properties owned by the estate of the Duchy of Cornwall.

Created in 1337 by Edward III for his son Edward, the Black Prince, the duchy’s main purpose has been to provide an income, independent of the monarch, for the heir apparent.

The Guardian also said the documents showed Charles, who holds the title Duke of Cornwall, also vetted the 2002 Commonhold and Leasehold Reform Act, which featured exemptions that favoured the duchy.

A Duchy of Cornwall spokesman said: “It is a long-established convention that the prince, as Duke of Cornwall, is asked by Parliament to provide consent to those bills which Parliament has decided would affect Duchy of Cornwall interests.

“If consent is required, draft legislation is, by convention, put to the Prince of Wales to grant solely on advice of ministers and as a matter of public record.”

The spokesman added: “The Duke of Cornwall nor the Duchy of Cornwall Council have any involvement in the drafting of legislation that relates (to) any part of leasehold reform including residential enfranchisement.

“The Duchy does, however, take great care to ensure that anyone purchasing a property where the freehold belongs to the Duchy is made completely aware of the restrictions that may apply to their property as a result of the legislation.”