Maurice Strong, the Canadian entrepreneur who stepped down from his job as the top international envoy for North Korea, broke United Nations rules by putting his stepdaughter on his diplomatic payroll, the UN says.

Kristina Mayo worked as her stepfather's UN assistant for two years before she resigned April 21 after the international organization learned about the family relationship, UN spokesman Farhan Haq said Friday.

The violation of staff regulations showed up after the inquiry into the Iraqi-oil-for-food scandal began investigating Strong.

Maurice Strong (CP file photo)

Strong has not been accused of any wrongdoing in the oil-for-food investigation, but he resigned as the special UN adviser on North Korea on April 20 after he was linked to a South Korean lobbyist who is suspected of bribing UN officials with Iraqi money.

Strong has acknowledged that South Korean businessman Tongsun Park invested money in Cordex Petroleums, a Calgary oil company that was run by Strong's son Frederick.

Park was accused in a U.S. federal court of allegedly receiving millions of dollars from Iraq to lobby illegally in the United States for the program, which allowed Iraq to sell oil while it was under UN sanctions between 1996 and 2003.