Yukio Hatoyama, leader of the Democratic Party of Japan, underlined Saturday his newfound resolve to challenge Prime Minister Junichiro Koizumi's structural reform drive.

Hatoyama told a party convention that the prime minister has failed to steer Japan out of the economic downturn in the eight months since he took office, in a reversal from Hatoyama's former position of broadly supporting Koizumi's reforms.

"Now I find Mr. Koizumi's reform measures are 'cold' ones," Hatoyama said to some 300 people attending the conference at a Tokyo hotel, criticizing the prime minister's policies and remarks over the structural reforms for lacking proper attention to the public.