An anti-monarchist group has called on the government to abolish the Duchies and for their land and revenue to be spent on local communities.

The Republic group has compiled a 29-page report, titled ‘Ditch the Duchies’, saying that there was also “clear evidence” that the Duchies of Lancaster and Cornwall are public property and not the private property of Charles and William.

Last year Prince William received a private annual income of more than £23m from the Duchy of Cornwall’s (DoC) land, most of which is in Devon and across the South West.

The business empire includes a portfolio of land, properties and assets, with the DoC being valued at more than £1bn.

But despite operating as a commercial venture and providing income for both Charles and William, the Duchies are run as private estates which are exempt from paying corporation and capital gains tax.

They are also separate from the Crown Estate, meaning the chancellor of the exchequer does not receive any of the Duchies’ profits.

But the report accuses the royals and the government of dishonesty about their ownership by claiming that they are 'private estates'.

The DoC was created in 1337 by an act of parliament. In 1669, it was also recorded in a parliamentary act that Charles II held the rights to rent from the DoC land “in Right of his Crown”.

According to Republic, this is confirmation that ownership of the Duchy “was in an official capacity and not a private capacity”.

The report said: “These are not the private property of the royals, but public assets that have been state property for hundreds of years.”

Speaking for Republic, Graham Smith said: “When the government claims to want to close a £22bn blackhole, how can we justify paying William £23.6m in 2024? How can we defend an annual income of more than £27.4m for our head of state, more than 159 times that of the prime minister?

“Charles and William receive the income only because they are monarch and heir, they do not own the duchies. This report puts any doubt about that to rest.

“We must be clear that there is a choice parliament can make: do we continue to provide gargantuan incomes to William and Charles via the duchies, or do we use those funds to invest in local communities.”

A recent investigation by Channel 4’s Dispatches and The Sunday Times revealed that the Duchies made about £50m in the past year alone from charging rent to the Ministry of Defence (MoD) the NHS, and schools and charities across the country.

In Devon, the DoC receives £1.5 million a year for the use Dartmoor Prison, which is currently closed.

Ratepayers in the South Hams are also paying the DoC millions of pounds in mooring fees as a result of a deal signed with South Hams District Council (SHDC) more than 15 years ago.

It also recently emerged that the Duchy was opposed to the opening of a cafe at the Princetown visitor centre, even though it could have generated income for the facility, which is due to close in October.

The report can be seen at www.republic.org.uk/duchies_report