WASHINGTON - Republican Sen. John McCain on Monday questioned President Obama about his political appointees' use of secret government email accounts at work, saying that Congress cannot tell the American people what its government is doing if it creates a "secret alternate communications network."

The letter from McCain, the senior Republican on the Senate's Permanent Subcommittee on Investigations, comes in response to an Associated Press report earlier this month that found that some top administration officials were using unpublished email accounts to conduct official business.

McCain said the practice undermines congressional oversight and complicates access to records under the Freedom of Information Act.

"Four years ago, you pledged to usher in a new era of government transparency. Since then, however, your administration has habitually circumvented congressional oversight," McCain wrote to Obama, alluding to past dust-ups between congressional Republicans and the president over access to executive-branch documents.

White House spokesman Jay Carney subsequently acknowledged the practice of having alternate accounts and said all emails - public or otherwise - were subject to congressional oversight. The White House did not immediately comment Monday on McCain's letter.

McCain asked Obama to answer several questions by July 1.

The National Archives and Records Administration's chief records officer, Paul M. Wester Jr., told The Washington Post on Monday that his agency is revising its guidelines to make sure that emails in nonpublic government accounts are preserved as required under the Federal Records Act.