Harare - Zimbabwean President Robert Mugabe, who read the wrong speech at the opening of parliament on Tuesday, must resign with immediate effect, the opposition Movement for Democratic Change (MDC), mled by Morgan Tsvangirai said.MDC spokesperson Obert Gutu said Mugabe had become "too old" to rule the country and must "immediately tender his resignation as the president of Zimbabwe"."At the very advanced age of 91, it has been proven, beyond a shadow of doubt, that Mugabe is way past his prime in that he failed to recognise that he was delivering the wrong speech... This is a sure sign of senility and grossly failing mental and physical health," Gutu said.Mugabe's spokesperson, George Charamba confirmed to the state-owned Herald newspaper that the nonagenarian had read the wrong speech.Charamba blamed a mix-up in Mugabe's office for the error. Old-age and ill-health"The mix-up happened in his secretarial office, therefore the delivery in parliament should be set aside. The error is sincerely regretted and corrective measures are being considered," Charamba was quoted as saying.Mugabe's speech was the same as the one he delivered during a state of the nation address (Sona) on August 25, in which he pinned his hopes on China to help revive Zimbabwe's struggling economy.Mugabe reportedly read the correct speech later at a Harare hotel.The Minister of Higher and Tertiary Education, Jonathan Moyo tweeted that Mugabe's delivery of the wrong speech was a "Big mix up" but not a "Big deal".Here is Pres Mugabe's right speech meant to be read yesterday. Big mix up, yes. Big deal, no! http://t.co/eV6DdF2FxW pic.twitter.com/My20VYyBjq— Prof Jonathan Moyo (@ProfJNMoyo) September 16, 2015A New Zimbabwe.com report said Mugabe, battling old age and ill-health, looked tired as he trudged through the inspection of the military parade before he delivered his speech.He was supposed to lay down the agenda for the first term's legislative sitting.A picture posted on Twitter by media owner, Trevor Ncube, showed a tired looking Mugabe walking into parliament.Am I the only one who thinks President Mugabe desperately needs to rest? Look at this picture. pic.twitter.com/aNZcvpJhTy— Trevor Ncube (@TrevorNcube) September 16, 2015Gutu said Zimbabwe did not deserve to continue under Mugabe's leadership."Zimbabwe doesn't deserve to be run by a nonagenarian president, who, in fact, is long overdue for retirement... The rigours of his presidential duties have certainly taken a toll on him and he should step down," said Gutu.