Japan will press ahead simultaneously with economic reform and constitutional changes as Prime Minister Shinzo Abe tries to revive his declining popularity, according to lawmaker Yasutoshi Nishimura, who advises the prime minister.

While Abe has vowed that he won't take his eyes off the economy, some investors have expressed concern that his determination to rewrite the nation's pacifist Constitution could come at the expense of further efforts to restructure the labor market and spur business investment.

"We can make progress on constitutional changes in parallel with economic and foreign policies," Nishimura, 54, said in an interview on Wednesday. "Economic growth is important and making wages rise will be the key. We will try to introduce policy measures that will lead to higher wages."