TOKYO — Spend big and never mind the deficit. That’s what proponents of modern monetary theory, the unorthodox set of economic ideas that has inspired politicians like Bernie Sanders and Alexandria Ocasio-Cortez, see as the winning formula for American prosperity.

For proof, its admirers point to Japan. Despite the highest debt in the developed world, Japan remains an economic powerhouse with high living standards.

Japanese leaders wish they would point somewhere else.

Shinzo Abe, the Japanese prime minister, has dismissed the theory as “simplistic.” Finance Minister Taro Aso described it as “very dangerous.” And Haruhiko Kuroda, the head of Japan’s central bank, called it “extreme.”

Rather than embrace an idea that could explain or even justify the country’s situation, Japan is furiously debating it. Lawmakers to Mr. Abe’s left are citing the theory — known as M.M.T. — to denounce his plan to raise taxes on the country’s consumers. On the right, members of his own party have tried to link his policies to the theory, accusing him of running up gargantuan debts the country can never repay.