Former U.S. vice-president Dick Cheney is blasting the Justice Department's decision to investigate whether CIA interrogators abused suspects detained after the Sept. 11, 2001, attacks. (Associated Press)

The decision to investigate whether CIA interrogators abused suspects detained after the Sept. 11, 2001, attacks is a purely political move that will have devastating effects on the spy agency's morale, former vice-president Dick Cheney says.

“I just think it's an outrageous political act that will do great damage long term to our capacity to be able to have people take on difficult jobs, make difficult decisions, without having to worry about what the next administration is going to say,” Cheney told Fox News in an interview on Sunday.

Cheney was responding to U.S. Attorney General Eric Holder's decision to look into a newly declassified 2004 report. The internal CIA inspector general's report revealed cases in which CIA interrogators threatened a detainee with a handgun and an electric drill, threatened one detainee with killing his family and staged a mock execution.

But Cheney said the allegations have already been investigated, and to launch a probe into actions reviewed by the Justice Department five years ago sets a “terrible, terrible precedent.”

Cheney said that some future administration could now come along “and rehash all of these decisions by an earlier administration.”

Agents will be hesitant to sign up for difficult missions, Cheney said, if they fear they are going to be subject to investigation and prosecution by the next administration.

“It's a very, very devastating, I think, effect that it has on morale inside the intelligence community. If they assume that they're going to have to be dealing with the political consequences — and it's clearly a political move. I mean, there's no other rationale for why they're doing this — then they'll be very reluctant in the future to do that.”

Cheney said the interrogation techniques were “good policy” and were “absolutely essential" in saving thousands of American lives and preventing further attacks.