Opposition parties shouldn't boycott Diet deliberations attended by two key ministers targeted by nonbinding censure motions in the Upper House in November, Chief Cabinet Secretary Yoshito Sengoku, one of those singled out, said Wednesday.

"If they boycott Diet deliberations because of the censure motions — a selfish strategy — the public will lose trust in politics and the Diet," Sengoku said during his first regular news conference of the year. "They should be very careful in engaging in such a tactic."

The Liberal Democratic Party and New Komeito, the two main opposition parties, have said they will boycott deliberations whenever Sengoku and transport minister Sumio Mabuchi, both of the ruling Democratic Party of Japan, are expected to attend.