An advocacy group on Monday sought a criminal probe of the White House over millions of possibly missing e-mails, saying someone may have deliberately deleted them to conceal involvement in a potential crime.

In a letter to Attorney General Michael Mukasey, Citizens for Responsibility and Ethics in Washington said the White House also may have violated two federal record-keeping laws, including the Federal Records Act, which carries criminal sanctions for unlawful destruction.

CREW, which is suing the Executive Office of the President, said over 10 million e-mails from March 2003 to October 2005 are missing. The period coincides with the runup to the Iraq invasion and the leaking by at least three top White House aides of the CIA identity of Valerie Plame.

The White House referred questions on the letter to the Justice Department, which declined immediate comment.

Asked last month about the possibility of missing e-mail, the White House said there is no reason to believe that any e-mails or other data are missing.

Two years ago, the prosecutor in the CIA leak probe of the Plame affair publicly revealed that the White House had a problem with its e-mail system, and that not all e-mail for the offices of the president and vice president in 2003 had been preserved through the normal archiving process.

In its letter to Mukasey, CREW asked the attorney general to appoint a special counsel, saying the Justice Department does not have the requisite independence to conduct an investigation of the White House.

At stake is the right of future generations to look back and understand the role of White House officials in critical events, said Melanie Sloan, CREW's executive director.