The leaders of major political parties faced off in a debate Sunday over the planned consumption tax hike and the pacifist Constitution, ahead of the start of official campaigning this week for the Upper House election.

In response to criticism from all five opposition party leaders, Prime Minister Shinzo Abe said during an online debate that there was no change in the plan to raise consumption tax from 8 percent to 10 percent in October.

"The consumption tax hike is necessary as a stable revenue source" for the government's plan to provide free education and child care programs, said Abe, who is president of the ruling Liberal Democratic Party.