ISLAMABAD: Pakistani Prime Minister Nawaz Sharif on Thursday for the first time explicitly dismissed a report from a corruption investigation that raised questions about the source of his family's wealth, rejecting it as slander. Sharif, 67, serving his third term as prime minister, faces opposition calls to step down but he was defiant in his condemnation of the report that alleges his family's income from business was not large enough to explain its wealth. A Joint Investigation Team (JIT), set up by the Supreme Court to investigate corruption allegations that surfaced following the Panama Papers leak, also accused his children, including heir apparent Maryam Sharif, of signing falsified documents about ownership of off-shore companies. 'The JIT report about our family businesses is the sum of hypotheses, accusations and slander,' Sharif said in a statement after meeting his cabinet. 'Accusations amounting to billions are being made here but no wrongdoing has been proven.' The investigation team, which included officials from a military intelligence agency, presented its report to the Supreme Court on Monday. Copies of it were then leaked to the media, prompting a chorus of demands from political parties that he resign from office. 'Nawaz's authority is completely eroded,' Shah Mehmood Qureshi, vice chairman of the opposition PTI party, told Reuters. 'There is no legal, moral or political justification for him to continue.' Pakistan has for decades been plagued by pervasive graft, and by rivalry between the military and civilian politicians. Worries Hit Stocks Sharif's term expires in June 2018 and elections are expected two months later. If he were forced to step down, his ruling PML-N party could appoint a new leader as prime minister until the polls. Nevertheless, worries generated by the 254-page report has sent stocks tumbling amid fears of chaos after several years of relative stability and accelerating economic growth. The economy expanded by 5.3 percent last fiscal year - its fastest in a decade. Big infrastructure investment by China has boosted growth while confidence has been buoyed by a decline in militant attacks. After years of electricity shortages and cuts, power outages have also been reduced but not eradicated. Sharif said the economic progress made since his election in 2013 showed the government was on the right track and any disruption would only hurt progress. 'We will not let darkness once again prevail in our towns and factories,' he said. Sharif, the son of an industrialist, will have his fate decided by the Supreme Court, which could disqualify him or order a trial. Sharif was originally nurtured by the military as a civilian politician who would protect their interests, and he served as prime minister twice in the 1990s. But he later fell out with an army chief and was ousted in a 1999 coup leading to a decade of exile. 'Our family has gained nothing from the politics, in fact it has lost a lot,' Sharif said.