Tutu was almost in tears and choked with emotion at a media briefing on Thursday after being asked by a journalist to comment on the NP's second submission to the TRC this week.
Tutu said he could not understand how De Klerk could still insist that he had been unaware of apartheid atrocities, when delegations from Lawyers for Human Rights and the Black Sash among many others had told him of security force involvement in gross human rights abuses.
Tutu said he himself had told De Klerk about allegations of security force involvement in the Boipatong massacre, after visiting survivors and hearing their stories.
"There was an avalanche of information. To say I did not know ..I find that hard to understand.
"I have to got to say that I sat there (at Wednesday's hearing) and I was close to tears. I feel sorry for him. I am devastated. (For him) to make an impassioned apology ... and then to negate it.
"All that is required is to say that `we believed in this policy but it is a policy that brought about all of this suffering. It is a policy that killed people. Not by accident,
Tutu said he had been deeply distressed by many of De Klerk's replies to questions put to him at the hearing.
"I had hoped there would have been the possibility of statesmanship."
TRC deputy chairman Dr Alex Boraine said De Klerk had contradicted himself when he first denied the NP had abandoned the security forces and then distanced the party from gross human rights abuses perpetrated by them.
"The security police (who have applied for amnesty) tell us they were carrying out the orders of their superiors. The generals tell us they were following the policy of the day.
"It is our view that the NP must accept political accountability for policies that would inevitably lead to atrocities. If you look at the legislation during the state of emergency, it was a licence to kill."
Tutu said he believed the commission had been even-handed in its treatment of the NP and the ANC submissions this week.
He said the ANC's submission was notable for its acceptance that it had committed human rights abuses which could not be justified.