Newly elected Democratic Party of Japan chief Seiji Maehara locked horns with Prime Minister Junichiro Koizumi for the first time in the Diet on Wednesday, with the opposition leader lashing out at the revived postal privatization bills.

Maehara argued that the postal bills will only create mammoth financial institutions under strong government control that private-sector firms will never be able to compete with on an equal footing.

"The funds held in postal savings are roughly equal to those deposited with the five major city banks combined, and the size of postal insurance is roughly equal to the four major life insurance companies put together," Maehara told a plenary session at the House of Representatives.