First Lady Akie Abe said Thursday her husband's administration should consider cutting wasteful spending and boosting the economy before going ahead with a rise in the consumption tax to 10 percent.

"Considering the falling birthrate and aging society, it probably can't be helped," she said in an interview at the prime minister's office, referring to an eventual rise in the sales tax, a question Prime Minister Shinzo Abe is now wrestling with.

"I think there are still areas where, if not a waste, taxes are not being used properly and could probably be fixed," she said.

"I can understand there are aspects that would be difficult if we don't raise the sales tax, but in my personal opinion, before doing that, shouldn't we put a bit of effort into the economy, fix what can be fixed and cut what can be cut?"

But she added: "This won't change just because I say so."

Her husband must decide by December whether to proceed with a second-stage rise in the consumption tax to 10 percent that is planned for October 2015 to help curb the huge public debt and fund the ballooning costs of the aging population.

But an initial rise to 8 percent from April triggered a sharp contraction in the economy in the three months to June, raising doubts about whether Abe should go ahead with the hike.

Mrs. Abe, who has be dubbed the "domestic opposition" for speaking out against some of her husband's policies, including nuclear power after the March 2011 Fukushima disaster, said she had urged the prime minister not to raise the levy to 8 percent back in April.

"I told him not to raise it," she said. Asked about this time, she said: "I wonder."