Japan was pitched into political crisis yesterday by the sudden resignation of Shinzo Abe, the Prime Minister, after months of Cabinet scandals and amid a bitter struggle over Japanese military support for the conflict in Afghanistan.

The mysterious departure of Mr Abe, two days after he had promised to fight on in the Diet, provoked rumours that he had suffered a mental collapse brought on by a combination of serious illness and an imminent financial scandal.

MPs were holding urgent talks last night to discuss who would succeed him as president of the ruling Liberal Democratic Party (LDP), the majority party in the Lower House of the Diet, the leader of which will thus automatically be elected prime minister.

Party members are likely to make their choice next Wednesday, and the strong favourite is the conservative nationalist Taro Aso, the secretary-general of the LDP and former Foreign Minister. However, such is the atmosphere of unpredictability and alarm in the LDP that the emergence of an outsider cannot be ruled out.

Mr Abe’s announcement of his resignation came out of the blue, shortly before he was due to appear in the Diet for questioning by MPs. “It’s now or never,” he said at a hastily arranged press conference. “If I postpone my resignation it will cause confusion, so I felt I had to do it as soon as possible. My presence is a ‘minus point’ and without me we can create a better [political] environment.”

His resignation speech, mumbled and punctuated with long pauses, referred to the Government’s difficulties in passing a Bill to extend the deployment of Japanese refuelling ships to the Indian Ocean, where they provide oil to US vessels supporting Nato troops in Afghanistan. The Bill is stubbornly opposed by the opposition Democratic Party of Japan (DPJ), which controls the Upper House.

“I made every effort to promote my reform agenda,” Mr Abe said. “But if I stay on as Prime Minister, we face a very difficult situation in dealing with the opposition party, and so we have to create new energy, and with it a new leadership.”

Even members of his Cabinet, reshuffled only 16 days ago, expressed shock at the announcement. On Monday, in his opening speech to the new session of the Diet, Mr Abe said that he had “set my mind on continuing my premiership”.

“It is the worst possible timing,” Gen Nakatani, the former Defence Minister, said. “Parliament has started and it’s now lost its leading act. There will be confusion, loss and trouble.”

Rumours and reports were circulating of a health crisis and an imminent scandal that had caused the Prime Minister to jump before he was forced out of office.

There have been rumours about Mr Abe’s health since he came to power a little less than a year ago. One Diet member from the ruling bloc told The Times last night that Mr Abe had successfully undergone surgery in the past for bowel problems, possibly cancer. “We expected that Mr Abe would resign sometime soon, but not soon after he said he’d stay on,” he said. “There is speculation that his health problem may have recurred.”

Last night the Mainichi newspaper reported a further possible explanation for the unexpected resignation: a political funding scandal of the kind that has already claimed four of his Cabinet ministers. According to the newspaper, the Weekly Gendai magazine has been investigating allegations related to the death of his father in 1991. The allegation is that Mr Abe transferred a 2.5 billion yen inheritance to his political support group without paying tax.

Mr Abe’s fall represents a triumph for Ichiro Ozawa, leader of the DPJ, whose victory in the Upper House elections in July give it a real chance of forcing a Lower House election and seizing power. He insisted yesterday that the DPJ would keep up the pressure to end the naval deployment.

A year of scandal

September 26, 2006: Shinzo Abe elected as Prime Minister

December 27, 2006: First Cabinet minister, Genichiro Sata, Administrative Reform Minister, resigns over alleged misuse of political funds

May 28, 2007: Toshikatsu Matsuoka, Agriculture Minister, commits suicide hours before facing questioning in Parliament over money scandals

June 30, 2007: The Government admits it has lost track of 64 million pension claims

July 3, 2007: Fumio Kyuma, Defence Minister, resigns after saying the US bombings in Hiroshima and Nagasaki in 1945 may have been inevitable

July 29, 2007: Mr Abe’s Liberal Democratic Party loses control of the Upper House to the Democratic Party of Japan

August 1, 2007: Norihiko Akagi, another Agriculture Minister, resigns following an accounting scandal in his office

September 3, 2007: Takehiko Endo, who lasted one week as Agriculture Minister, resigns over misuse of farm subsidies

September 12, 2007: Mr Abe announces he will resign

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