Lusaka - Future Zambian presidents will have to garner at least 50% of the popular vote to be elected and their powers will be significantly curbed, according to an apparent leaked draft of the new constitution.
The text - published by online publication Zambian Watchdog and the Lusaka Times - appears to be a final draft drawn up by a team of experts, which President Michael Sata has sought to keep unpublished.
The proposed law would significantly curb the power of his office, and demand winning presidential candidates "receive more than fifty percent of the valid votes cast."
If no candidate manages to secure 50% of the vote, a two-person run-off will be held.
The switch from a first-past-the-post to a run-off system and moves to set up a constitutional court have elated civil society organisations, which described the text as "beautiful".
The constitutional court would have the power to hear cases involving the president and vice-president.
Would-be presidents would also have to appoint a running mate, rather than appointing the vice president after assuming office.
The leak appears designed to force the hand of Sata, who fought calls from civil society and religious groups to have the technical committee publish their draft.
"Clearly, there are provisions within the draft that Sata does not like and just as clearly, he was hoping to bury it - or use the time to rewrite the offending sections," said Zarina Geloo of the Open Society Institute for Southern Africa.
Earlier this month Sata said his Patriotic Front government was "duty bound to protect the masses" from those that have "hijacked" the drafting process.
"It will be highly irresponsible for us as people's representatives to authorize the release of this document before it goes through cabinet," he said.
Presidential aides said the government had not yet received the draft.
"We urge the technical committee to come out clean on claims that the document [it is] entrusted with has been leaked," said presidential advisor George Chellah.
Civil groups in Zambia welcomed the draft.
"This is a beautiful document and it meets the aspirations of the Zambian people," said Andrew Ntewewe of the NGO Yali.
"If this document is authentic, then it explains the PF's adamant [refusal] to release it."