"I would very sadly not be able to vote for them after the way things have gone," the 81-year-old retired South African archbishop wrote in South Africa's Mail and Guardian newspaper.
"The ANC was very good at leading us in the struggle to be free from oppression. But it doesn't seem to me now that a freedom-fighting unit can easily make the transition to becoming a political party."
Tutu called South Africa "the most unequal society in the world."
Tutu, who was awarded the 1984 Nobel Peace Prize for his efforts to end South Africa's apartheid, was also strongly critical of past decisions made by the ANC government at the United Nations, particularly on Zimbabwe, the BBC noted.
"The things we have voted for or against have been a disgrace. It has been a total betrayal of our whole tradition," he wrote.
The BBC noted that in 2011, Tutu accused the ANC government of "kowtowing" to China by holding up a visa for the Dalai Lama, the Tibetan Buddhist leader who had been invited to attend the archbishop's 80th birthday celebrations.