Wickremesinghe is also the minister in charge of the Central Bank of Sri Lanka, and has been accused of appointing his close friend Arjuna Mahendran as its governor despite a conflict of interest involving Mahendran's son-in-law's links to primary dealer firm Perpetual Treasuries.
Perpetual Treasuries was alleged to have made thumping profits in two central bank bond issues in February 2015 and March 2016. The opposition has dubbed this as the "biggest financial scam in Sri Lanka's history".
"I had an opportunity to explain our government policy on public debt...," Wickremesinghe said as he left after testifying.
"The president, secretary of our party and our ministers have come forward to fearlessly give evidence," he said, adding, "the 'yahapalanaya' (good governance) will move forward. There is nothing to hide. There may have been mistakes, shortcomings, but the 'yahapalanaya' will move forward".
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The opposition has called for Wickremesinghe's resignation over the alleged scandal.
Wickremesinghe was summoned before the commission following his public announcement last month that he was willing to testify should the commissioners require any clarification from him about government policy on bonds.
Sirisena appointed the three-member commission in January to investigate whether the country lost billions of rupees, as claimed by the opposition, as a result of inside information leaked to a primary dealership linked to Mahendran's son-in- law.