Wickremesinghe's party has a majority in parliament and Sirisena's bid to bring back the country's former strongman Mahinda Rajapakse has already failed
President Maithripala Sirisena on Sunday reignited the power struggle that has crippled Sri Lanka's government for more than a month, vowing never to reappoint arch-rival Ranil Wickremesinghe as prime minister.
Wickremesinghe's party has a majority in parliament and Sirisena's bid to bring back the country's former strongman Mahinda Rajapakse has already failed.
But Sirisena choked back tears in a meeting with foreign correspondents as he accused Wickremesinghe, who he sacked on October 26, of being "highly corrupt."
"Even if the UNP has the majority I told them not to bring Ranil Wickremesinghe before me, I will not make him prime minister," he said, referring to Wickremesinghe's United National Party.
"Not in my lifetime," he added.
Sirisena dismissed Wickremesinghe following a host of personality and political clashes since they formed a coalition in 2015. He named Rajapakse as new premier and tried to dissolve parliament but the Supreme Court and legislators blocked the president's moves.
Wickremesinghe, who occupies the prime minister's residence, and Rajapakse, who has the premier's official offices, have both refused to back down.
But the country officially has no prime minister, heightening international fears about Sri Lanka's stability and looming foreign debt repayments.
Sirisena told foreign correspondents at his official residence that he will appoint a commission to investigate corruption under Wickremesinghe since January 2015.
"He is corrupt. His economic policies are not good for local industries. He pursed an extremely liberal form of government that is not compatible with our culture."
Sirisena fought back tears as he recalled how he asked Wickremesinghe to step down in February when their respective parties were beaten in local council elections.
"I told him that we lost the election because his economic policies had failed. I told Ranil in this very room to step down, but he refused," Sirisena said.
He added that there had been "over 100 instances" of open clashes between the two and that their power struggle had become an open secret in the cabinet.
Sri Lanka's parliament meets on November 27 and 29 to discuss a motion by the UNP to cut off government spending.
Government finances will stall on January 1 unless a 2019 budget is passed.
If the UNP wins the vote, it could force Rajapakse to withdraw his claim to the leadership, and make Sirisena to name a prime minister from the party.
"If the UNP shows a majority, I believe Mahinda will do the right thing (and stand down)," said Sirisena, although he reiterated that he would still not reappoint Wickremesinghe.
Sirisena insisted that it was not a personality clash but a "disagreement over policy."
Asked if he could constitutionally ignore the leader of the largest single party in parliament, Sirisena said he would rely on tradition.
"There is a tradition that the person appointed PM should be able to work with the president. I cannot work with Ranil. The UNP will have to bring somebody else."