TOKYO - Japan's ruling coalition on Tuesday sought to speed up the search for a successor to beleaguered Prime Minister Yoshiro Mori soon after the budget bill passes as his public support sank to a new low, according to AFP reported.

As calls for Mori's resignation grew within the coalition, former prime minister Ryutaro Hashimoto acknowledged at a news conference that "the situation is very severe."

"Considering these opinions, we have to think about how to organize the convention" to be held by Mori's ruling Liberal Democratic Party (LDP) on March 13, Hashimoto said.

The convention is widely seen as a key event, where Mori is expected to be pressed openly to quit by party members now campaigning for his ouster ahead of an upper house election in July.

Hashimoto, state minister in charge of administrative reform, is a possible contender to replace Mori, who has been under fire over gaffes and scandals, AFP said.