The leader of Japan's main opposition party, Seiji Maehara, has said he will resign following a scandal over a false accusation against the ruling party.
Seiji Maehara had only been in the job for six months
Last month the opposition admitted that allegations made by a DPJ MP - that the son of a ruling party member was linked to a disgraced company - were untrue.
The party has already apologised over the incident.
Mr Maehara told officials at a meeting on Friday that he was stepping down to take responsibility for the scandal.
DPJ CRISIS TIMELINE
September 2005: DPJ hit by election loss - Seiji Maehara appointed party leader
13 February 2006: Livedoor boss Takafumi Horie charged with breaking securities law
16 February: Hisayasu Nagata makes allegation during parliamentary meeting
28 February: Mr Nagata and DPJ announce email was faked, issue public apology
14 March: DPJ places apology in six national newspapers
31 March: DPJ leader Seiji Maehara resigns
"It is my responsibility that the problem was not dealt with immediately," he told reporters after his announcement.
Other senior Democratic Party of Japan (DPJ) officials, including Secretary-General Yukio Hatoyama, also planned to step down, according to party officials. A new leader would be elected on 7 April, officials said.
Mr Maehara said he hoped his decision would help the party win back public trust. "It is good for the Democratic Party of Japan to restart with a new line-up after my resignation," he said.
The controversy began when a member of the DPJ said he had an email which proved links existed between the beleaguered head of internet company Livedoor, Takafumi Horie, and the son of the secretary general of the ruling Liberal Democratic Party (LDP).
Lawmaker Hisayasu Nagata told parliament that Mr Horie asked Livedoor officials in an email to pay 30m yen ($255,700) in consulting fees to the son of Tsutomu Takebe, Reuters news agency reported.
But the allegation proved to be unfounded, with Mr Nagata unable to verify the authenticity of the email. Reports in the Japanese media suggested the faked email had come from a journalist.
The DPJ withdrew the allegations and issued a public apology earlier this month. Mr Nagata has since been suspended from his party.
Mr Horie and four of his executives have been under arrest since January on charges of breaking securities laws.
Mr Horie ran as a ruling party candidate in September 2005 polls
The Livedoor head ran as a candidate for the ruling LDP in the September 2005 general election but was not successful. LDP leaders have faced criticism over their association with Mr Horie since the allegations against him emerged.
Analysts suggest the DPJ was keen to gain public support by demonstrating deeper links between the ruling party and the disgraced executive.
The DPJ has struggled since September 2005 polls in which the party lost more than 60 seats.
Mr Maehara was chosen to lead the party after Katsuya Okada's resignation over the damaging election result, and had cast himself as a fresh start for the beleaguered party.
The BBC's Jonathan Head in Tokyo says the DPJ must now try to find new leaders in its ranks who can revive the party's fortunes in time to challenge the successor to Prime Minister Junichiro Koizumi, who steps down in September.