The real cost of the Royal Family to taxpayers is £510m a year - nearly six times more than the £86m of state funding from the annual Sovereign Grant - anti-monarchy campaigners say.

The Sovereign Grant covers costs such as staffing, travel and the upkeep of royal buildings - but not security, for example.

And for security alone, the Republic group says - while calling on the government to provide a definitive figure - £150m is "indicative of a likely cost" based on press reports.

Keeper of the Privy Purse Sir Michael Stevens, who looks after the King's financial affairs, has previously spoken of the "determination to deliver value for money" in royal finances.

But Republic chief executive Graham Smith said: "How can we talk about cutting the winter fuel allowance while wasting half a billion pounds on the royals?"

The group's £510m figure also includes "lost income", such as the £96m a year commercial revenue it says could come from royal residences.

It also says the duchies of Lancaster and Cornwall's property businesses should be paying into the public purse rather than funding the King and the Prince of Wales respectively, with the taxpayer losing out on £99m per year.

Republic attacks the current funding for the royals as opaque and secretive and a "scandalous abuse of public money".

A head of state should have running costs of £5m-£10m a year, it says, and the King should have an annual salary of £189,000, with increases pegged to that of the prime minister.

Buckingham Palace has declined to respond.

But the latest accounts for the Sovereign Grant, published in July, show state funding for the Royal Household will remain at £86.3m for 2024-25 and rise to £132m in 2025-26.

The level of funding is calculated against the profits of the Crown Estate, with next year's rise reflecting increased income from offshore wind farms.

"This is now the third year for which the Sovereign Grant has not increased by one single penny, despite the supplementary costs incurred by the change of reign and despite the double-digit inflationary pressures that have impacted on goods and services for all organisations in that same period," Sir Michael said earlier this year.

"What has remained constant is the determination to deliver value for money in ensuring the Royal Family are able to serve our communities to the best of their abilities, even in difficult personal circumstances."

Significant divides

As well as costs, there are also harder-to-measure economic benefits from the royals, such as boosting tourism and supporting overseas trade.

Last month, 55% of those surveyed by YouGov viewed the monarchy as good value for money, while 30% saw it as poor value.

• The institution was seen positively by 59%, negatively by 32%
• The King was seen positively by 63%, negatively by 29%

But below these headline figures, there are significant divides, particularly in terms of age groups, with support for the monarchy strongest among older people and opposition strongest among the young.