“When the devil offers you immunity, you would be a fool to enter what is called a Faustian bargain,” he told BBC Hardtalk’s Zeinab Badawi.

He described President Emmerson Mnangagwa's government as being an "illegal regime".

"They are afraid of elections. They do not want to have free and fair elections let alone credible elections," Mr Moyo, who is in self-imposed exile, said.Mr Mnangagwa and his deputy, former army chief Constantino Chiwenga, visited opposition leader Morgan Tsvangirai last week in the hope of winning his support for the postponement of general elections due in August, Mr Moyo added.

"We know that when Mnangagwa and Chiwenga went to Morgan Tsvangirai's house they pretended that they were concerned about his health but we know they wanted to negotiate with him to postpone elections for at least three years," he said.