The office of former President Lee Myung-bak threatened to take legal action Sunday against a weekly over an article that alleged Lee laundered prize money he received from the United Arab Emirates.

The office expressed deep regret and demanded Weekly Hankook take "appropriate steps" over its report uploaded on its website Saturday that said Lee laundered $500,000 through Nonghyup Bank, a local banking unit of state-run Nonghyup Financial Inc.

"We have no choice but to take legal action unless reasonable steps are taken," the office warned in a written message.

The weekly deleted its report on Lee, though it did not give any explanation for taking down the story.

The office said the prize money was deposited in an account pursuant to protocol, and is set to be used for its intended purposes -- Lee's environmental project.

Nonghyup Bank also said that the prize money had nothing to do with money laundering and that the transactions were carried out in the normal way.

In 2011, Lee was presented with the Zayed International Prize for the Environment, along with the prize money to be used toward his "low-carbon, green growth" campaign that calls for sustainable economic growth by reducing greenhouse gas emissions.

The UAE launched the award in 1999 to commemorate its first president, Sheikh Zayed bin Sultan Al Nahyan, a pioneer who turned the desert country into an environmentally friendly nation.

Lee, who served president between 2008 and 2013, was in hot waters for his controversial big-budget project to refurbish the country's four major rivers. (Yonhap News)