Former US defense secretary Donald Rumsfeld admitted in an interview that the country "would've been better off" if he had quit after the 2004 Abu Ghraib scandal and spared no criticism of his colleagues in his new memoir published Tuesday.

In "Known and Unknown," Rumsfeld defends his handling of the war and recounts his government career serving Republican presidents from Richard Nixon to George W. Bush.

However the former Pentagon chief also admitted his biggest error during his tenure under Bush was his failure to convince the president to accept his resignation in the wake of the Abu Ghraib prison scandal.

"That was such a stain on our country. To think that people in our custody were treated in that disgusting and perverted and ghastly way - unacceptable way," Rumsfeld told ABC News anchor Diane Sawyer.

And so I stepped up and told the president I thought I should resign. And I think probably he and the military and the Pentagon and the country would've been better off if I had," he said.

The comments came in his first television interview since leaving public life in December 2006 after a long and divisive tenure at the Pentagon.

In his memoir, Rumsfeld meanwhile wrote how he was "surprised and troubled" that US interrogators went further than the controversial methods of detainees at Guantanamo or Abu Ghraib prison in Iraq that had been otherwise approved.

Rumsfeld Regrets: Not Quitting After Abu Ghraib