TOKYO - A SENIOR Japanese lawmaker threatened on Monday to leave the ruling party in a blunt show of defiance against unpopular Prime Minister Taro Aso on the first day of a high-stakes parliamentary session.

Former reform minister Yoshimi Watanabe said he had sent a letter to Prime Minister Taro Aso urging him to call snap polls and to scrap a plan to send out cash rebates totalling US$21.7 billion (S$31.9 billion) to boost the ailing economy.

'If my proposals are not swiftly and sincerely reviewed and deliberated, the letter says that I, taking the just path, shall leave the Liberal Democratic Party,' Mr Watanabe told reporters.

Mr Watanabe, whose father was a prominent LDP lawmaker and former foreign minister, has pushed Mr Aso to call elections to seek a popular mandate for a party that has switched premiers three times in little over two years.

However, polls have shown the ruling bloc risks suffering a landmark defeat because of Mr Aso's low popularity and public concern over the recession and a widening gap between rich and poor.

The LDP has been in power continuously since 1955, except for a period of 10 months in the early 1990s.

'Politics nowadays pays too much attention to the interest of the party. I say we must look at things from the eyes of the people,' Mr Watanabe said.

His remarks came hours after parliament opened a session that will look at budget proposals, including the rebates, which Mr Aso says will stimulate spending but critics call a gimmick that will worsen Japan's debt-ridden finances.

In an interview with AFP in December, Mr Watanabe said that Japan will see an 'inevitable' transformation of its political landscape with the next election, which is due by September.

Along with Mr Watanabe, several liberal-leaning LDP lawmakers have formed 'study groups' widely seen as laying the groundwork for an independent party. -- AFP