Saudi Arabia businessman, one of the most influential in the Middle East, says he has been undervalued by $9.6bn

For most people, even featuring in the Forbes list of the world's billionaires would be cause for celebration, but for Prince Alwaleed bin Talal of Saudi Arabia, appearing at number 26 with $20bn (£15bn) was an insult.

The prince, one of the most influential businessmen in the Middle East, insists the list undervalues him by $9.6bn. He has vowed to sever all ties with the group's reporters and accused them of damaging US-Saudi relations.

In response, the editor of the influential list has written a stinging rebuke saying the prince considers a top-10 ranking one of his priorities, systematically exaggerates his wealth and spends more time and effort than any other businessman on attempts to boost his ranking – even more time and effort than Donald Trump.

Forbes's estimate of Alwaleed's wealth at $20bn puts him behind Google founders Larry Page and Sergey Brin. But Alwaleed, a nephew of the Saudi king whose investments are run by his Kingdom Holding Company, estimates his own wealth at $29.6bn (£19.5bn), which would catapult him into the top 10 of the magazine's richest people on the planet, just behind 90-year-old French cosmetics heiress Liliane Bettencourt.

Forbes said the prince's camp wrote four letters in the build-up to the list's publication in an effort to secure a favourable valuation. In one letter his chief financial officer, Shadi Sanbar, said an undervaluation "strikes in the face of improving Saudi-American bilateral relations and co-operation. Forbes is putting down the Kingdom of Saudi Arabia and that is a slap in the face of modernity and progress."

But Forbes hit back, with billionaire list editor Kerry Dolan explaining it no longer considers the share price of Alwaleed's Saudi-listed Kingdom Holdings an accurate reflection of its value.

She points out that the share price would soar by up to 136% in the weeks before Forbes locked in the valuation to calculate its rankings in the past three years.

Dolan wrote: "The value that the prince puts on his holdings at times feels like an alternate reality, including his publicly trading Kingdom Holdings, which rises and falls based on factors that, coincidentally, seem more tied to the Forbes billionaires list than fundamentals."

In a scathing character assassination, the writer describes the prince as a vainglorious businessman in the "absurdly opulent" surroundings of his marble-clad palaces filled with portraits of himself. "If he needs to go on a business trip, he has his own 747, à la Air Force One, except unlike the president, his plane has a throne."

During a trip to Riyadh in 2008, the article said, he showed off his wealth, including what he claimed was a $700m haul of jewels, and sent the magazine's US offices mocked up copies of Vanity Fair, Time 100 and Forbes magazine itself with his face adorning the front covers, according to Dolan.

"Of the 1,426 billionaires on our list, not one – not even the vainglorious Donald Trump – goes to greater measure to try to affect his or her ranking.

"In 2006 when Forbes estimated that the prince was actually worth $7bn less than he said he was, he called me at home the day after the list was released, sounding nearly in tears."

Shares in Kingdom Holdings, his vehicle for investments in Citigroup, Newscorp and Apple, among others, would rise in the 10 weeks before the Forbes list was finalised.

In 2010 its shares rose 57%, despite shares in Citigroup falling 20% in the same period. In 2011 the same happened, with a 31% rise in Kingdom's shares, and in 2012 they jumped 136%.

A former Alwaleed executive told Forbes that market manipulation in Saudi Arabia was rife. The magazine quoted the executive as saying: "This is the national sport … There are no casinos. It's the gambling site of the Saudis."

The prince, who enjoys the nickname "the Buffett of Arabia" after shrewd investments in eBay and Apple, called the allegations "completely unsupported and biased".

A statement added: "The application of differing standards of proof for different individuals and organizations results in an arbitrary and confusing set of standards that seems demonstrably biased against the Middle East."

Sanbar, chief financial officer of Kingdom Holding, said: "We have worked very openly with the Forbes team over the years and have on multiple occasions pointed out problems with their methodology that need correction.

"However, after several years of our efforts to correct mistakes falling on deaf ears, we have decided that Forbes has no intention of improving the accuracy of their valuation of our holdings and we have made the decision to move on."

He said they would now focus on working with Bloomberg Billionaires index, a Forbes rival launched last year, which estimates the prince's wealth at $28bn, ranking him not in the top 10, but the world's 16th wealthiest person.

A princely sum

Prince Alwaleed bin Talal boasts that Forbes has referred to him twice as "one of the world's most intelligent and creative investors". On his website he claims to have met more than 250 heads of state and world leaders and says: "As a man of significant wealth and influence, Prince Alwaleed is humbled when people look to him for advice and guidance on issues such as religion, global peace and how society should adapt to meet the challenges of the 21st century."

The Saudi prince, 57, owns 95% of the Kingdom Holding Company, which trades on the Saudi stock exchange. As well as shares in companies such as News Corp and Citibank it holds stakes in a string of luxury hotels including the Savoy in London, the George V in Paris and the Fairmont Raffles.

The company started investing in Apple in 1997, the year Steve Jobs returned to the helm of the company he founded. It recently bought an estimated 3% of Twitter for $300m (£230m) and has stakes in AOL and Motorola.

Not all his investments have been a great success. In 1997 he bought a stake in TWA, which declared chapter 11 bankruptcy in 2001 and merged with American Airlines. Another notable failure was Kodak, which went bust last year, overwhelmed by the digital photography revolution.

He invested in Euro Disney in 1994, and in 1995 helped complete Canary Wharf by putting in cash when the owner was in receivership. The group holds a third of Jeddah Economic, which owns the project to build the 1,000-metre, $1.2bn Kingdom Tower in Jeddah.

The prince also holds an 80% stake in Rotana, one of the Middle East's biggest media companies.

His 200 cars include a Rolls-Royce Phantom and Lamborghinis and Ferraris. His fleet of private jets includes a Boeing 747, an Airbus 321 and a Hawker Siddeley 125.

According to Forbes he was the first individual to buy an Airbus A380 double decker plane and was supposed to take delivery of it this spring, but Kingdom Holding's chief financial officer told the magazine that the plane has been sold.