The consumption tax needs to be more than doubled to shore up the government's finances, given soaring debt and welfare costs, according to a member of Prime Minister Naoto Kan's tax and social security panel.

"I don't think an increase to 10 percent is enough," former financial services minister Hakuo Yanagisawa said Tuesday in an interview at his Tokyo office. "Our discussions must be based on new realities."

Kan appointed the 75-year-old Yanagisawa to the panel that will meet for the first time this Saturday. Yanagisawa is a former colleague of economy minister Kaoru Yosano, who is leading Kan's push for a debate on the 5 percent consumption tax and has advocated doubling the levy.