By Sarah Marsh BUENOS AIRES (Reuters) - President Mauricio Macri, who won last year's election in Argentina partly on promises to fight corruption, on Monday denied any wrongdoing in his connection with an offshore company in the Bahamas which emerged in a leak of documents. Macri was among the tens of thousands of rich and powerful people named in the leak of four decades worth of documents from Mossack Fonseca, a law firm based in the tax haven of Panama which specializes in setting up offshore companies. The "Panama Papers" showed that he moonlit as director of Fleg Trading Ltd, which was founded in 1998 and dissolved in January 2009. Opposition lawmakers demanded on Monday that he explain his role at the offshore company. In a short television interview with La Voz, Macri said that his tycoon father Franco Macri, one of the richest men in Argentina, had founded the company through a "legal operation". "It was an offshore company to invest in Brazil, an investment that ultimately wasn't completed, and where I was director," he said. "There is nothing strange about this." The Panama Papers were leaked to more than 100 news organizations around the world cooperating with the U.S.-based International Consortium of Investigative Journalists (ICIJ). While holding money in offshore companies is not illegal, journalists who received the leaked documents said they could provide evidence of wealth hidden for tax evasion, money laundering, sanctions busting, drug deals or other crimes. In its online report, the ICIJ highlighted that Macri had not disclosed his connection with Fleg Trading Ltd in his assets declarations after he became Buenos Aires mayor in 2007. The Macri administration said late on Sunday Macri had never had a stake in the firm so he had not been required to disclose the connection in those declarations. "To create a company in a tax haven is not a crime in and of itself," the head of the Argentine anti-corruption office, Laura Alonso, wrote on Twitter. Alonso is a member of Macri's party and her swift defense of the president prompted outcry from opposition lawmakers, including calls for her resignation. "She came out immediately defending the president when her role is to investigate whether an act of corruption was carried out," the Front for Victory said in a statement, calling for the anti-corruption office to be headed by the opposition. (Additional reporting by Nicolas Misculin; editing by Grant McCool)