Former US vice-president Dick Cheney today launched a forthright public attack on Barack Obama's administration, saying decisions to close Guantánamo Bay and outlaw harsh interrogation methods had left the United States more vulnerable to the risk of a terrorist attack.

In an interview also remarkable for the strenuousness with which he sought to defend George Bush's foreign policies, Cheney claimed the US had achieved "what we set out to do" in Iraq, and that the war had been "worth doing" because it had eliminated "the biggest threat" America faced in the wake of the 9/11 attacks.

After two months during which he has kept a low profile, Cheney surfaced to give his first televised interview since leaving office to CNN's John King, who asked him if he thought Obama's reversal of numerous Bush-era detention practices had made the US less safe.

"I do," Cheney replied. The new president, he added, was "making some choices that in my mind will raise the risk to the American people of another attack".

Obama has ordered the closure of the detention camp at Guantánamo Bay, and of secret CIA prisons around the world, and has banned controversial interrogation methods such as waterboarding, widely regarded as a form of torture.

On Friday, the White House announced that it would stop using the phrase "enemy combatant" to describe Guantánamo detainees, and would base its treatment of them on international law, a change of course that several human rights groups said did not go far enough. But Cheney insisted the Bush administration's approach to detention had been "absolutely essential to the success we enjoy, of being able to collect the intelligence that led us to defeat all further attempts to launch attacks against the United States since 9/11. I think it's a great success story. It was done legally, it was done in accordance with our constitutional practices and principles."

The former vice-president also sided with a minority of Americans in describing the Iraq war as worthwhile, claiming that the problems the US had encountered there were "secondary" to the "basic result" of removing Saddam Hussein. "I think it was absolutely the right thing to do, and I think when history reviews this period 10 or 20 years hence, what will be significant was that we did, in fact, accomplish what we set out to do," he said.

"We have succeeded in creating, in the heart of the Middle East, a democratically governed Iraq. And that's a big deal."

The war, he maintained, had eliminated the possibility of "a terror-sponsoring state with weapons of mass destruction … providing those to a terrorist organisation."

In a wide-ranging fusillade against Obama, Cheney also criticised his choice of ambassador in Iraq, Christopher Hill, calling him inexperienced, and said the president was using the recession to try to justify "one of the biggest expansions of federal authority … in the history of the republic".

He dismissed the idea that the Bush administration was to blame for the current crisis as "interesting rhetoric".

Cheney diverged from total support for Bush only over his former chief of staff, "Scooter" Libby, who was convicted of perjury and obstruction of justice. Bush spared Libby from prison, but Cheney said the president's failure to pardon him had left him "hanging in the wind".

Devon Chaffee, an attorney with Human Rights First, which campaigns on national security issues, said: "The interrogators and former military leaders we've spoken to just don't believe that the so-called 'enhanced' interrogation techniques were effective – they made us less secure, not more secure."