The US Justice Department has opened an investigation into the leak of a CIA agent's identity, US President George W. Bush's spokesman said today.
"The president has directed the White House to co-operate fully with this investigation," spokesman Mr Scott McClellan said.
The controversy centers on the disclosure that Ms Valerie Plame - the wife of Mr Joseph Wilson, a former US ambassador to Gabon - was an undercover CIA operative specialising in weapons of mass destruction.
Mr Wilson believes his wife's cover was blown by administration officials seeking to discredit him or get revenge after he accused the White House of exaggerating the threat from Iraq.
Justice Department lawyers notified the White House counsel's office last night that it had begun an investigation into "possible unauthorised disclosures concerning the identity of an undercover CIA employee," according to a memo sent to White House staff by counsel Mr Alberto Gonzales.
Mr McClellan said all staff were directed to preserve all materials that could be relevant to the investigation. This would include phone logs and e-mail.