Ministers who spoke to The Zimbabwean off the record this week said they had asked him to step down.
But Information Minister Webster Shamu dismissed the call, saying there was "no basis" for the president to leave office.
Mugabe travelled to Singapore again last week for what his administration claims is an eye problem. It is his seventh state-funded trip this year, each one costing the taxpayer an estimated $3million in travel and medical expenses.
Finance minister Tendai Biti last week lamented budget overruns on travel, and said the GNU had so far blown $40million on travel.
Shamu insisted the president "has not been found incapable of discharging his functions”.
A Zanu (PF) minister said the president's illness "has created a dangerous situation whereby no-one is in charge of the affairs of state during his absence". Prime Minister Morgan Tsvangirai has not been permitted to exercise full executive authority during Mugabe's absences, and Cabinet does not meet when he is away.
Another minister spoke of "a vacuum of leadership" whereby ministers are "engaged in infighting" and "routinely flout the orders of the president".
An MDC minister Mugabe was an obstacle to peaceful transition. "We need to carry out the necessary transformation needed for the economic, social and political recovery of Zimbabwe, and for that to happen Mugabe must go," he said.
The ministers’ words reflect the general mood in the country, where there is real concern that the president's recurring health problems have rendered him unable to do his job. Upon his return from the UN General Assembly, he looked very frail, with acute hair loss.
According to confidential US embassy cables wired to Washington and leaked by whistleblowing website Wikileaks, Mugabe is plagued with cancer which has metastasised to other parts of his body.
"According to Gono, Mugabe’s doctor had recommended he cut back on his activities," reads part of the 2008 cable. "Gono told us last year that Mugabe was ill and that his doctor had urged him to step down immediately. Mugabe told his doctor, according to Gono, that he would leave office after the election."
One minister said Zimbabwe risked ending up with a Woodrow Wilson or Kamuzu Banda scenario where the incapacitated head of state in effect surrendered the running of affairs of state to their wives. Mugabe's wife Grace is 40 years his junior, but maintains a low profile.
Qhubani Moyo, an executive member of Welshman Ncube's MDC, said perhaps Mugabe was clinging to power so that he could hand the baton to his son Chatunga.
Political analyst Ibbo Mandaza said the issue was of profound national importance and authorities must come clean on the 87-year old leader's health.
"It is a matter of serious public interest,” he said. Zimbabwe’s current The constitution provides for a joint committee to be set up upon the request of only one-third of MPs to look into the President’s health.Post published in: News