COLOMBO, Sri Lanka — Sri Lanka’s Parliament debated a no-confidence motion against Prime Minister Ranil Wickremesinghe on Wednesday, a move that threatens the unity government elected on a platform of good governance.

A vote on the motion, brought by a group led by former strongman Mahinda Rajapaksa, was expected later in the day. Wickremesinghe needs 113 votes in the 225-member Parliament to defeat the motion.

The main allegation involves his appointment of a Singaporean as the central bank governor who is now accused of leaking inside information to benefit his son-in-law in a treasury bond sale.

Sri Lankan police have sought Interpol assistance to arrest Arjun Mahendran, the former bank governor. His son-in-law and another official are already under arrest.

According to a presidential commission’s findings, Mahendran’s son-in-law allegedly made profits of $72 million from the dealings while the state lost about $55 million.

The no-confidence motion has threatened Sri Lanka’s unity government, formed by parties that are traditional rivals led by Wickremesinghe and President Maithripala Sirisena, with parts of Sirisena’s party mulling voting against the prime minister. A victory for the motion would boost Rajapaksa’s plan to recapture power.

Opposition lawmaker Dinesh Gunawardena opened the debate, saying Wickremesinghe was responsible for the scam because he appointed a foreigner to head a sensitive institution such as the central bank, and that its impact has been felt in the country’s economy, with low investor confidence.

Government Minister Lakshman Kiriella defended Wickremesinghe, saying two inquiries into the bond scam — one by a parliamentary committee and the other by the presidential commission — found no fault with the prime minister.

Minority leader Rajavarothayam Sampanthan, who heads the largest ethnic Tamil party in Parliament, said his party will oppose the motion because it wants the president and the prime minister to implement their pledge to draft a new constitution protecting the political rights of minority Tamils after a protracted civil war that ended in 2009.

He said Rajapaksa’s supporters want to unseat the government because they don’t want the government’s pledge implemented.

“They want to first defeat the prime minister. The next target will be the president; they want the government brought down,” Sampanthan said.

“We want the government to implement the mandate given to it by the country. In these circumstances how can we support this no-confidence motion?”

Rajapaksa was defeated in the 2015 presidential election after Sirisena, who was his health minister, defected and joined Wickremesinghe in an election alliance.

After being elected president as a neutral candidate, Sirisena accepted an offer from Rajapaksa to take over his Sri Lanka Freedom Party. Since then, party rivalries have been simmering within the government.

Despite giving up party leadership to Sirisena, Rajapaksa is now leading a splinter Freedom Party group in Parliament.