A Saudi billionaire is suing American magazine Forbes for libel, alleging it wrongly put his true wealth at $9.6 billion less that it is in a rich list.

Prince Alwaleed bin Talal, a grandson of Saudi Arabia's founder and nephew of King Abdullah, had attacked its ranking of world billionaires as flawed and biased against Middle Eastern businesses after he was ranked number 26 – with a value of $20bn –this year.

He filed a defamation suit against Forbes, its editor Randall Lane, and two of its journalists on April 30 at the High Court in London. Details of the claim were not immediately available.

Prince Alwaleed owns large stakes in Citigroup, News Corp and Apple Inc, among other companies. He is also owner or part-owner of luxury hotels including the Plaza in New York, the Savoy in London and the George V in Paris.

This year's Forbes World Billionaires list was published in March. Forbes stands by its estimate.