"Once we see the prospects of a recovery from several angles, the current policy can be ended," Taya, the newest member of the central bank's policy-setting committee, told business leaders in a speech. Taya's hawkish comments come as the financial markets try to decipher the BoJ's deliberately murky definition of when it will end its 15-month-old zero rate policy. The BoJ has vowed to keep rates at zero until "the prospect is in sight" of an end to fears of deflation in the world's second biggest economy.

Since last month, bank Governor Masaru Hayami has begun to say the conditions to end the policy were falling into place. He said that an end to the long decline in personal incomes would be the key to judge whether deflation has abated, but markets continue to wonder how the bank would determine this.

Hayami has emphasised such spending data as bonuses, wages and overtime pay but Taya seemed to sound a warning that the market should not view any indicator as decisive and give the central bank more room to manoeuvre."It is not the case that the bank would not change policy until a recovery is confirmed after the fact in private demand, as represented by business fixed investment or private consumption," he said. One sign of recovery likely to please the restless BoJ is wage earners' income, which rose for the fifth straight month in April.

Taya cited this data, saying prospects for a steady rise in employment incomes were bright, although risks remained for income from extra benefits and compensation, such as bonuses.

But overtime pay -- another set of data that economists say is linked to consumption -- rose for the 12th consecutive month in April, gaining 4.2 percent from a year earlier.