"SADC [Southern African Development Community] should never have recognised Mugabe as legitimate," Skelemani said.
"[They] should treat Mugabe and the MDC [the opposition Movement for Democratic Change] as equals because none of them have won elections."
Skelemani said that if the SADC did not bring pressure on Mugabe, then the grouping should be held responsible for any deaths in Zimbabawe.
"The best solution would be to pressurise Mugabe as an international community to go for a [presidential] run-off. So that the Zimbabweans, the only ones entitled to choose a government for Zimbabwe, can do so," he said.
"My suspicion is that Mugabe would not agree because he is sure to lose," Skelemani said, adding that, in such a situation, supplies to Mugabe should be cut off - for instance, petrol for his army.
International condemnation
The call followed Gordon Brown, the British prime minister, condemning Mugabe's "blood-stained regime" and Condoleezza Rice, the US secretary of state, saying that it is well past the time for Mugabe to quit.
Raila Odinga, the Kenyan prime minister, said on Sunday that Jakaya Kikwete, Tanzania's president and chairman of the African Union, should call an urgent summit of AU states to formulate a resolution sending troops to Zimbabwe.
"If no troops are available, then the AU must allow the UN to send its forces into Zimbabwe ... to take control of the country and ensure urgent humanitarian assistance to the people dying of cholera and starvation," Odinga said in Nairobi, Kenya's capital.
EU foreign ministers are expected to adopt a draft text tightening sanctions against Zimbabwe on Monday, due to fears over the worsening humanitarian situation and political deadlock in the country.
Mugabe and his wife Grace, as well as 166 other members of the ruling Zimbabwean regime, are already banned from entering EU nations and their European assets have been frozen.
This list is expected to be added to on Monday.
EU sanctions blamed
Harare has blamed EU sanctions for a cholera outbreak across the country which is thought to have killed at least 575 people.
Mugabe accused Zimbabwe's former colonial ruler Britain of using the epidemic to draw together support against his regime.
An editorial in the state-run Sunday Mail newspaper also said the outbreak was down to EU sanctions.
"The people who are suffering most are not politicians they claim they want to punish, but poor people," it said.
"All the victims [of cholera] are as a result of the freezing of balance of payments support, depriving the country of foreign currency required to buy chemicals to treat our drinking water."
The outbreak has followed a political crisis since elections in March and a subsequent failure to agree on a power-sharing deal.
Mugabe lost initial presidential elections to Morgan Tsvangirai, the MDC chief.
Tsvangirai pulled out of a second run-off poll in June due to attacks on his supporters which were blamed on Mugabe's allies, handing Mugabe victory.