The Bank of Japan's brief political honeymoon ended abruptly on Friday when the architect of Junichiro Koizumi's economic reforms described the central bank's monetary policy guidance as "well short of satisfactory".

Heizo Takenaka, the interior minister and former economy minister, said the bank's intention of making policy based on the "understanding" that price stability lies in the range 0-2 per cent did not meet its "obligation for accountability".