His comments follow an attempt this week by the ANC to block the release of the Truth and Reconciliation Commission's report.
"Sycophants are the worst possible thing to have around you when you are in power," Tutu told the Sunday Times.
He said those who forgot the past were doomed to repeat it.
His comments come at the end of a week in which the TRC reported on how the apartheid government had conducted a reign of terror against its citizens.
The newspaper said Tutu sounded his strongest warning yet against the formerly oppressed imitating those they had toppled.
"The price of freedom is eternal vigilance and there is no way in which you can assume that yesterday's oppressed will not become tomorrow's oppressors. We have seen it happen all over the world and we shouldn't be surprised if it happens here," he said.
He called on churches and the media to keep a vigilant watch on the ruling party.
"We so easily jettison the ideals we had when we were struggling. It is important that we retain the vigour of our civil society organs that were part of the struggle."
He added: "We've got to retain the same capacity to smell out corruption, the abuse of power... If they (the government) are the true democrats which we hope they are, they will say: `Those are in fact our true friends - the ones who tell us when things are not right'."
Following the release of the TRC's report on Thursday, Tutu was scheduled to travel to the United States on Saturday.