Samura Kamara served as Minister of Finance and then Minister of Foreign Affairs under President Ernest Bai Koroma (2007-2018). He was defeated by current President Julius Maada Bio in the 2018 presidential runoff. He is considered the main competitor of Bio, who has also declared himself a candidate.
This comes as a Sierra Leone court on Thursday began a corruption trial against the main opposition party's candidate in this year's presidential election, opening the way for the possible invalidation of his bid.
The High Court had earlier on Thursday rejected an appeal to throw out the allegations against Samura Kamara, who this week was chosen as the All People's Congress (APC) candidate for the June presidential poll.
A conviction would prevent Kamara from running for president and holding public office.
A former foreign and finance minister under ex-president Ernest Bai Koroma, Kamara is viewed as the main rival to current leader Julius Maada Bio, who will stand for re-election.
In December 2021, he was charged with misappropriating more than $2.5 million in public funds in a case tied to planned refurbishments to a New York consulate while he was foreign minister.
The High Court on Thursday rejected a "no-case submission" presented by the APC's lawyers and asked Kamara to put up a defence case against the corruption allegations in a trial.
Kamara was in the court for the ruling in the capital Freetown, with the building heavily guarded by security personnel, and his trial was adjourned to March 17.
Bio defeated Kamara in the second round of the 2018 presidential election and launched an anti-corruption campaign in the small West African country, where graft is considered to be endemic.
Several senior officials from the Koroma administration have since been targeted, but the APC has denounced a "witch hunt".