Pop diva Madonna has weighed in on Malawi's chaotic election, criticising embattled President Joyce Banda, who has tried to nullify the vote amid allegations of irregularities. The superstar, who adopted two children from the southern African nation, has been involved in a long-running spat with Malawi's government over her charity work in the country. In a statement posted on the website of her charity Raising Malawi, Madonna accused the government of corruption and of failing its people. "I am so sad to see that because of the actions of their president Malawians will continue to suffer," the American singer said. "In my philanthropic work I have seen the depths of corruption in Malawi's government. I can only hope that change will come, Malawians deserve so much better." The remarks come after Banda attempted to declare the presidential election "null and void", prompting fierce legal wrangling over her right to do so. A week after Malawians went to the polls to elect a new president the result is still not known and fierce legal wrangling has raised the prospect of a protracted political crisis. With at least 90 percent of the votes counted over the weekend, it was unclear if election watchdogs would release the results, and if the outcome would be recognised. - 'Serious irregularities' - President Banda has said the vote was marred by "serious irregularities," calling for the election to be re-run within 90 days. She said on Saturday that she would not stand as a candidate in such a re-vote, to "give Malawians a free and fair" election. It is not clear if she has the constitutional power to make such a move and a court ordered the vote count to continue. Malawi's electoral commission has admitted problems -- in some places the number of votes cast is greater than the number of voters -- but efforts to stage a recount have been blocked by a court order at the request of opposition leader Peter Mutharika. On Friday with about a third of the votes counted, Mutharika had 42 percent of the vote, with Banda on 23 percent. On Saturday Mutharika avoided claiming victory but said the "people have spoken and this was a free and credible election". Banda's supporters believe the vote was far from fair, and fear the 74-year-old brother of late former president Bingu wa Mutharika may be attempting to steal power. Peter Mutharika already faces treason charges for attempting to conceal his brother's death in office two years ago, as part of an alleged plot to stop Banda -- then vice-president -- from assuming power as directed by the constitution. Amid the electoral confusion there are fears of political violence and the US, UN and EU have called for calm. "We urge all political leaders and their supporters to refrain from violence, and to resolve any disputes in a manner that adheres to Malawi's laws and its constitution,"  State Department spokeswoman Marie Harf said in a statement Monday. UN Secretary General Ban Ki-moon reiterated his call to the candidates and their supporters "to respect the ongoing tallying process, follow existing legal procedures to resolve any electoral challenges or complaints," a UN spokesman said. The election imbroglio is unlikely to help Malawi's dire economic problems. After taking office Banda oversaw the devaluation of the kwacha currency by 50 percent, the easing of foreign exchange restrictions, and the raising of fuel prices and cutting of subsidies. That helped restore an IMF credit line, but the country remains overly dependent on agriculture and foreign aid to survive. Madonna's charity says it has poured millions of dollars into the support of children, including orphans in Malawi, which is ranked by the UN Human Development Index as one of the world's 20 least developed countries. But after a visit to the country last year Banda's government accused the 55-year-old of inflating the value of that help, demanding VIP treatment, being "uncouth" and bullying state officials.