The head of a US congressional subcommittee is asking a federal agency to investigate whether Afghanistan President Hamid Karzai is misappropriating foreign aid funding to benefit himself and his family.

Representative Dana Rohrabacher announced on his website that he has requested an investigation by the US Government Accountability Office.

The request for an investigation coincides with consideration in Congress of President Barack Obama's 2013 budget proposal that includes $2.5 billion for Afghanistan.

Rohrabacher's March 7 letter to the comptroller general of the Government Accountability Office asked for a report to Congress on US foreign aid funds that "have been stolen, diverted or otherwise inappropriately gone to, or benefited Afghan President Hamid Karzai and his family."

Rohrabacher is chairman of the House Foreign Affairs subcommittee on oversight and investigations.

"American taxpayer money must cease being diverted and abused by the leader of a country whose people America has tried so valiantly to help," Rohrabacher's letter said. "A report that thoroughly quantifies how much US foreign aid has gone to the Karzai family is urgently needed."

He cited media reports and Wikileaks cables as sources for his allegations.

The New York Times reported March 7 that Karzai's brother, Mahmoud Karzai, received interest-free loans to buy a stake in the Kabul Bank, where the allegations of financial corruption are centered.

They involve suspicions that bank and government officials skimmed foreign aid money intended to support US and coalition forces in Afghanistan.

The bank came close to insolvency but was bailed out by the Afghan government with funds partially subsidized by Western nations.

"It is time to know for sure, on the record, exactly how dishonest the government in Kabul has become and how much money we are wasting there," Rohrabacher wrote.