"This is either a massive cover-up or an incompetence that is not acceptable service to the American people," he said on CBS's "Face the Nation."
McCain said that information that has surfaced since the attacks, which claimed the lives of four Americans, including U.S. Ambassador Chris Stevens, indicates the narrative provided by the White House in the days following was "patently false."
The White House initially claimed that the attacks on the consulate in Benghazi were sparked by spontaneous anger over an anti-Muslim film created in the U.S., but later said the attack had been planned and carried out by armed militants.
The administration has said their public statements on the attack were based on the intelligence that was then available.
President Obama's handling of the situation has become a campaign issue, with Mitt Romney and congressional Republicans accusing him of waiting too long to call the assault a terrorist act and questioning if the administration downgraded security ahead of the violence.
The issue has provided the Romney campaign an opening on foreign policy, an issue that the Obama team saw as a strength thanks to the president’s drawdown of troops from Afghanistan and Iraq and the successful mission to kill al Qaeda leader Osama bin Laden.
And McCain, in his advice to Romney, indicated foreign policy should become a larger part of the discussion in the waning days of the campaign.
"I think that national security, as I said, foreign policy has entered into this discussion," he said.