The Democratic Party of Japan's new president on Tuesday named Goshi Hosono as party policy chief and appointed Akira Nagatsuma and Renho as deputy presidents.
Katsuya Okada's appointment of prominent party figures presents an image of unity as the DPJ tries to regain public trust.
Hosono, a former DPJ secretary-general, and Nagatsuma, a former health minister, lost to Okada in Sunday's party presidential election.
Renho is known for grilling bureaucrats over wasteful public spending when the DPJ held power between 2009 and 2012.
Okada told reporters he was able to set up a strong executive board, one capable of taking on Prime Minister Shinzo Abe's Liberal Democratic Party.
Okada previously headed the DPJ between May 2004 and September 2005. He has already decided to retain Yukio Edano as his No. 2, the party's secretary-general.
Liberal Democratic Party Secretary-General Sadakazu Tanigaki reacted by saying the DPJ has assembled a strong team of leaders.
"From what I've seen in the past, I believe they have abilities to criticize or attack the ruling camp," Tanigaki told reporters.
LDP Vice President Masahiko Komura had a similar reaction, saying the team could criticize the ruling bloc and urged his party to prepare for a possible grilling.
"Many of them are skilled at rhetoric," Komura said during an LDP executive meeting Tuesday morning, adding that the party needs to support ministers speaking about administration policy.