The estimate, made by the Finance Ministry, underscores the difficulty of fixing Japan's tattered finances, which are now the worst among major developed nations.
If the government does not cut spending, raise taxes or find more non-tax revenues, new bond issuance could even rise as high as 54.2 trillion yen ($659.2 billion) by the year ending in March 2015, according to the estimate, the Nikkei said.
The government plans to issue 44.3 trillion yen in new bonds, within its self-imposed target for fiscal 2011/12, which will be debated in parliament now in session.
One of the key pledges by Prime Minister Naoto Kan, who is struggling to keep the fragile economy afloat while reining in Japan's huge public debt, has been to limit new government bond issuance at or below 44 trillion yen.
Evidence that the government won't be able to rein in Japan's debt burden, the worst among industrialised countries, could put further pressure on Kan's cabinet to trim spending, scale back welfare benefits and boost taxes.
The government needs to cut spending by 1.1 trillion yen for fiscal 2012/13 and 0.8 trillion yen for fiscal 2013/14 to be in line with guidelines adopted last June that cap policy-related spending at 70.9 trillion yen in each of the three years to fiscal 2013/14, the Nikkei said.
But even if the government achieves these spending cuts, new bond issuance will come to 49.8 trillion yen for fiscal 2013/14, the business daily said.