A former national security adviser, Richard Clarke, today endorsed Governor Spitzer’s divisive effort to make it easier for illegal immigrants to obtain drivers licenses.

“States should act to register immigrants, illegal and legal,” Mr. Clarke, who served as a top advisor to presidents Bush, Clinton, and Bush, said in a statement. “From a law enforcement and security perspective, it is far preferable for the state to know who is living in it and driving on its roads.”

The statement came as Mr. Spitzer spoke at the New York University for Law and Security to rally support for the license plan, which has been attacked by state republicans who argue the plan would threaten national security.

Mr. Clarke drew national attention when he alleged the Bush administration could have taken more measures to prevent the terrorist attacks of September 11, 2001 in his book “Against All Enemies.”

“Here’s a person, who at a critical time in our nation’s history, had the courage to stand up and say the hard truths that no one wanted to say,” Mr. Spitzer said.

Mr. Spitzer contends that his opponents don’t understand that anti-fraud measures in his plan will make the system the most secure in the nation.