Japan's lower house of parliament has approved Prime Minister Yoshihiko Noda's controversial plan to double sales tax.

日本议会众议院通过了首相野田佳彦加倍征收营业税的计划。

Japanese broadcaster NHK reported that 57 ruling party lawmakers failed to back the bill.

These included party founder¹ Ichiro Ozawa, who has indicated he could form a new political party.

If others were to follow him, Mr Noda could be forced to call an election.

Mr Noda says doubling the tax from 5% to 10% by 2015 is key to cutting Japan's high public debt and funding rising welfare costs.

The two main opposition² parties supported the bill, which still needs to pass the upper house to become law.

Ahead of the vote, Mr Noda appealed for support. "This reform is not just for our generation, but for our future," he said in a final pitch to parliament.

Aging population

The controversial tax hike has seen bitter disagreement and gridlock amongst Japan's lawmakers.

The cabinet approved an outline of the bill in February but has been mired³ in negotiations⁴ since.

Mr Noda says raising sales tax - called consumption tax in Japan - is key to addressing Japan's financial woes⁵ and funding the needs of its aging population.

Japan estimates that 40% of its population will be of retirement⁶ age by 2060 - meaning the taxes of far fewer workers supporting far more retirees.

Several Japanese prime ministers have mooted⁷ the idea of raising sales tax in the past, but the move has proved deeply unpopular with voters.

Mr Ozawa, who has been leading the charge against Mr Noda over the tax hike, is a veteran politician leading the biggest fraction within the DPJ.

He was cleared of charges in a long-running political funding scandal in April.