"We need someone like that who is highly placed to tell us what's really going on. We know that we were misled on Iraq," McGovern told Fox News Radio.
McGovern, a former senator, unsuccessfully ran against Richard Nixon for the White House in 1972.
Deep Throat, revealed this week as former FBI assistant director Mark Felt, acted as a source to The Washington Post newspaper, helping to bring down Nixon's presidency over the Watergate scandal in 1974.
Worse than Nixon
"I wish there were somebody of the Deep Throat time in this administration who are aware of what's going on," McGovern told Fox News Radio.
"We have an administration in power now that led us to a war that is internationally illegal"
1972 US presidential candidate
"This war in Iraq, in my opinion is worse than anything Nixon did. I think Nixon deserved to be expelled from office in view of the cover-up that he carried on and the laws that he violated.
"But we have an administration in power now that led us to a war that is internationally illegal; it's a war that we are fighting with a country that has no threat to us that has nothing to do with the 9/11 attacks.
McGovern said Nixon was undoubtedly "tricky", but said of Bush: "This man claims to be Christian, following the will of God, and then he misleads the whole nation on a totally fraudulent enterprise in Iraq that we should have never been attached to."