TAIPEI (AFP) - Taiwan's President Ma Ying-jeou on Wednesday categorically denied a report that he holds a US green card and owes the US government Tw$500,000 (S$21,000) in taxes, saying he would resign if the claim turned out to be true.

The report, appearing in the latest issue of Taiwan's Next Magazine, alleged that Mr Ma holds US permanent residency and is therefore subject to the US Foreign Account Tax Compliance Act.

The law, effective from January 2014 and known worldwide as Fatca, requires US citizens, green card holders and other taxpayers abroad to report their income to the Internal Revenue Service (IRS), the US government agency responsible for tax collection and enforcement.

Mr Ma has previously said he renounced the US green card he obtained two decades ago as a student in America, and he swiftly rebuffed the Next Magazine report. "President Ma had made it clear when he was campaigning for the presidency in 2008 that he had already renounced the green card that he obtained as a student in the United States more than 20 years ago," presidential spokesman Li Jia-fei told reporters. "Since it has long become invalid, the president is absolutely unlikely to pay tax to the US authority," she said. "President Ma would like to shoulder full political responsibility and resign if it turned out to be true."

Ms Li accused the magazine of basing its report on incorrect information, saying the name on the president's green card had been "Ying-jeou Ma", while the magazine referred to a "Mark Y.J. Ma".

The magazine also claimed Mr Ma's birthday was July 12, 1950, when in fact it is July 13, she said. "The magazine will have to take legal responsibility for its malicious intention to mislead the public," she said.

Mr Ma's 2008 presidential rival, Frank Hsieh of the Democratic Progressive Party (DPP), had questioned his loyalty to Taiwan over the green card issue. The DPP had also said it suspects that Mr Ma, who studied graduate law at New York University and Harvard, is a US citizen. Under Taiwan's election laws, anyone holding foreign citizenship is ineligible to stand for president.

Mr Ma has said his US residency became void a long time ago, and he has since applied for tourist visas to the country.

Mr Ma was elected in 2008 on a platform of beefing up trade and tourism ties with China. He was re-elected in January 2012. Beijing views Taiwan as part of its territory awaiting reunification, by force if necessary, although the island has been self-governing since its split with the mainland in 1949 at the end of a civil war.