Nkala, who fell out of favour with Mugabe after the notorious Willowgate car scandal exposed by verteran journalists, Geoff Nyarota, said : "Zanu PF is an old party for old men.
There is no thinking in Zanu PF and everybody is afraid of Robert Mugabe. In fact it should be called Robert Mugabe (Private) Limited and not Zanu PF. I am afraid that after or when President Mugabe dies he will go down the grave with the party."
Nkala was responding to reports that Mugabe would be the candidate for Zanu PF in the next election.
Nkala, who also served as Finance Secretary in Zanu PF said he had no regrets that he had left Zanu PF.
"Everybody in Matabeleland and in fact in Bulawayo supports Dumiso Dabengwa because he is a Ndebele. Zanu PF brought about tribal politics in Zimbabwe because it is for the Zezurus only."
Dabengwa has broken away from Zanu PF and has revived Zapu.
Nkala said Zanu PF would lose seats in Matabeleland because it was very unpopular there.
Nkala was booted out of government by President Mugabe after the Willowgate Motor Car scandal during the 1980s.
He is now retired and staying at his farm in Matabeleland.
Meanwhile sources say Mugabe is expected to meet several heads of state and government in Copenhagen to try and tell them the Zimbabwe story.
"President Mugabe will use this opportunity to meet with big bosses in Copenhagen," a close source said. "This is the biggest conference in the world and will allow him to meet leaders he would otherwise never meet. People are worried about the huge amount of money being spent but Zanu PF is not worried because this is a PR exercise for them."
He said Mugabe would also meet SA boss, Jacob Zuma as well as the SADC heads.
Mugabe and a large entourage left for Copenhagen on Monday night after allegedly diverting an Air Zimbabwe plane, a move that caused Prime Minister Morgan Tsvangirai to abandon the trip.
Tsvangirai is said to have said the country could not afford to have a large entourage attending the world summit at a time when the country is battling to survive financially.