"When the South African government denied His Holiness the Dalai Lama a visa to attend the Nobel Laureates Summit in Cape Town last year, I called them a lickspittle bunch," said Tutu in a statement.
"Our police minister's performance in clearing the President of any responsibility for the Nkandla spending, gave new meaning to the word."
South Africa's ombudswoman last year found that President Jacob Zuma had "unduly benefited" from the work on his private residence at Nkandla -- which also included a cattle enclosure, amphitheatre and visitors' centre -- and recommended that he repay some of the money.
The swimming pool was actually a "firepool" needed to fight any blaze at the mainly-thatched compound, while the cattle enclosure and chicken run were necessary to prevent the animals tripping motion detectors as they roamed about, the minister concluded.
But Tutu dismissed the minister's conclusions.
"Instead of setting a good example, our public representatives are humiliating themselves, our country and our people by trying to defend the indefensible," said Tutu.
"It is unconscionable to spend hundred of millions of rands on the president's spurious 'security' needs," said Tutu.
"The power of the government to manipulate justice comes at great cost to our reputation, our development potential and our hard-won self-belief.
"I am deeply saddened," added the Archbishop, who is regarded internationally as a moral authority.