Mugabe was "defiant and angry" in the interview aired on Thursday, telling journalists his wife Grace had had to save the lives of some of his ministers during the military takeover.
Speaking to the South Africa's SABC at his Blue Roof mansion in Harare, Mugabe called Emmerson Mnangagwa's takeover a disgrace.
On the other side of town, the UNDP chief Achim Steiner earlier met Vice-President Constantino Chiwenga, the former army chief who played a leading role in ousting Mugabe.
Steiner also held talks with Foreign Minister Sibusiso Moyo and repeated the UN’s willingness to help Zimbabwe prepare for elections later this year.
Under Mugabe the UNDP was due to fund the procurement of biometric voter registration kits to draw up a new and tamper-free voters’ roll, RFI correspondent Ryan Truscott says.
But early last year Mugabe’s government suddenly announced it would pay for the kits itself, in an about-turn that critics saw as evidence that the ruling party did not want a transparent process.
Mnangagwa is striking a much friendlier, open note than his predecessor, saying Mugabe, as a private citizen, has the right to free speech.
But Mugabe is clearly unhappy and unwilling to accept what has happened.
In a separate development, Foreign Minister Moyo said his country was holding consultations on rejoining the Commonwealth.
Mugabe pulled Zimbabwe out of the 53-nation bloc in 2003 after he was criticised over disputed elections and violent seizures of white-owned farms.