Japan's Justice Minister Koizumi Ryuji has left the Nikai faction of the main ruling Liberal Democratic Party after prosecutors raided the group's office due to a fundraising scandal.

Tokyo prosecutors searched the offices of the LDP's Abe and Nikai factions on Tuesday in connection with suspected violations of the political funds control law. Koizumi belonged to the Nikai faction.

On Wednesday, Koizumi submitted a request to leave the faction, saying he wanted to avoid any potential conflict of interest as the justice minister has authority over investigations by the prosecutor-general.

The Nikai faction accepted Koizumi's request.

The minister told reporters that considering it is the Justice Ministry's duty to perform its work in a fair manner strictly based on the law, he left the faction so as not to invite any misunderstandings among people.

Koizumi added that he did not leave the faction just temporarily.

Referring to opposition parties' calls for his resignation, the minister said he will do his best in carrying out the duties given to him.

Meanwhile, the opposition camp agreed to take a united front in demanding that Koizumi step down as justice minister, saying it is not appropriate for him to remain in the post as he belonged to the Nikai faction.

Last week, Prime Minister Kishida Fumio replaced four Cabinet ministers and five state ministers who belong to the Abe faction. But he said he intended to retain two ministers from the Nikai faction, including Koizumi, in his Cabinet.