Social Democratic Party (SDP) Vice President Seiji Mataichi said on Sunday that Prime Minister Yukio Hatoyama is not qualified to be Japan's leader.

The SDP deputy chief made the remarks in response to Hatoyama's call for the SDP to stay in his tripartite ruling coalition.

"...he (the premier) is not qualified to be a state leader as he has lost his perspective," Mataichi told reporters.

On Saturday SDP leader Mizuho Fukushima said she plans to propose that the SDP leave the tripartite government coalition led by Hatoyama's Democratic Party of Japan (DPJ).

The SDP is scheduled to hold a meeting of executives at 1 p.m. Sunday with the key topic being whether to stay in ruling coalition.

On Friday, Hatoyama sacked Fukushima as the consumer affairs minister from his cabinet as the SDP chief refused to sign the cabinet resolution on the issue concerning the relocation of the U. S. Futenma base.

In August last year, the DPJ won a landslide victory in the historic lower house election, putting an end to more than 50 years of almost uninterrupted rule by the LDP.

A handsome victory as it was, cooperation with the two allies is needed for the DPJ to control the less powerful upper house to ensure smooth legislation.

In September, the DPJ and its two smaller allies -- the SDP and the People's New Pary (PNP) -- agreed to launch a tripartite coalition government in a party chief meeting attended by DPJ President Hatoyama and his SDP and PNP counterparts Fukushima and Shizuka Kamei.