Former LDP policy chief Shizuka Kamei officially declared Wednesday that he will run in the Sept. 20 party presidential election, seeking to unseat Prime Minister Junichiro Koizumi.

Kamei, the outspoken coleader of a 59-member intraparty faction within the Liberal Democratic Party, promised to pursue an economic policy diametrically opposed to Koizumi's.

He is advocating a fiscal spending package worth tens of trillions of yen in an effort to boost demand.