The artist Damien Hirst is now so rich he’s a dollar billionaire, according to his manager. From a few old fish and some restaurant detritus, Hirst has apparently created an empire that will soon be worth more than Sotheby’s if it keeps growing at this rate.

In an interview ahead of a huge sale of new Hirst works, Frank Dunphy, who handles the artist’s affairs, claims Hirst is the “biggest dollar earner in the history of art”, is worth “a billion” and has invested widely in property. In fact, he has so many properties he’s lost track of the number he owns.

The Hirst estate ranges between 30 and 40 properties, according to Dunphy, including a £3m country pile in Gloucester and a couple of Georgian houses in Mayfair.

If accurate, the sums would propel Hirst, 43, into the ranks of the richest 150 people in the country. He would be more than twice as wealthy as Sir Mick Jagger and Sir Elton John, and on a par with the Harry Potter writer JK Rowling.

Like the merit of Hirst’s art, the claims about his wealth divide observers. Simon Lee, one of London’s top dealers who represents the American pop artist Cindy Sherman, said: “I’m sure he is worth a billion.” His gives the figure credence based on Hirst’s cult status.

“It’s like Jackie O and Andy Warhol combined,” said Lee.

Angus Maguire, art adviser at Bloomsbury Auctions, said: “If Hirst is worth a billion now, it’s fair to say that he’s going to be worth far more over the course of his career, not to mention the kind of value his work is going to have after his lifetime.”

However, one sceptic said: “Damien’s greatest work of art is rapidly becoming his bank balance. There’s a whiff of pickled shark about it.”

The 2008 Sunday Times Rich List calculated Hirst’s fortune at £200m. Researchers could find only modest value in his company, Murderme, which had assets of just £12.4m in 2004-5.

The main basis of his wealth was his large art collection, which was valued at £100m.

What Hirst’s art is worth – and who owns it – is a moot point, even between him and Dunphy. Last year the Hirst sales machine put a price tag of £50m on a diamond encrusted skull he sold to an investment group. However, last week Hirst said he had retained ownership of a third of the skull.

Confusingly, Dunphy, who began his career as an accountant for circus clowns, said Hirst still owns two-thirds of the skull and that it is now worth £150m. Doubters might argue that anyone smart enough to create a skull that valuable ought to know who owns it.

Hirst is putting 223 new works up for sale at Sotheby’s in London later this month. New works are usually sold through dealers, who take a commission. By selling at auction he is hoping to make more for himself.

One of the lots is a charolais bull pickled in a golden glass case; its estimate is £8m-£12m. In total, the sale could realise £60m or more.

Richard Wentworth, the sculptor who taught Hirst in the early 1990s at Goldsmith’s College, south London, said: “The art world’s a marketplace, the world is a dosh pit and we’re all in it. We’re coming to the end of a stage in western civilisation of vulgar, vulgar, vulgar. With this sale, Damien has just added one more thing, PS, vulgar!”

As for Hirst’s wealth, Wentworth said: “It’s sweet. It’s like a little boy stamping down the street, yelling, ‘I’m worth a billion dollars’.”

DAMIEN’S TRIUMPHS

For the Love of God
Diamond-encrusted skull, sold for £50m

Lullaby Spring
A cabinet containing medicines, made £9.65m

The Physical Impossibility of Death in the Mind of Someone Living
A 4.3 metre-long tiger shark in formaldehyde, fetched £4.5m

Editor's choice

• U2 at Nou Camp Stadium, Barcelona
• The 50 Best Movie Villains
• The 15 golden rules of theatre etiquette