Koizumi ally sues over sex claims

Yamasaki says the allegations are groundless

A key political ally of the Japanese prime minister is seeking damages for libel over a magazine article containing lurid details of an alleged 10-year relationship with a woman claiming to be his mistress.

The 65-year-old politician, Taku Yamasaki, is secretary-general of the governing Liberal Democratic Party.

The article is completely groundless and greatly damages Taku Yamasaki's character, reputation and political trust

LDP Secretary General Yamasaki's office

His office said the article in the weekly Shukan Bunshun was totally groundless and seriously damaged the political trust in Mr Yamasaki, as well as his character and honour.

The magazine's chief editor, Seigo Kimata, said the publication had voiceprints, handwriting samples and other evidence, including pictures, to back up its allegations.

"Mr Yamasaki should make an upright decision (whether to resign his LDP post) by considering stopping hurting this woman who has been trampled upon," Mr Kimata said.

Prime Minister Junichiro Koizumi told reporters the scandal was just "a private matter" and did not go any further.

Elections

The article comes days before the LDP faces key tests in two parliamentary by-elections on Sunday.

Defeat would further damage Mr Koizumi's standing with the party and the public.

Mr Yamasaki, an important Koizumi ally, is expected to come under pressure to resign if the LDP fares badly in the elections.

Koizumi's popularity has been damaged by scandal

Candidates are vying for an Upper House seat in the north-western prefecture of Niigata and a Lower House seat in Wakayama, near Kyoto.

A new governor of Tokushima prefecture, in western Japan, is also being selected after the former incumbent was arrested for allegedly accepting bribes.

LDP scandals have already taken their toll on the prime minister's popularity.

Opinion polls suggest public support for Mr Koizumi, which reached 80-90% when he first took office a year ago, now stands at about 40%.

Earlier this month, Koichi Kato - another close ally of the prime minister and a predecessor of Mr Yamasaki - resigned from parliament over a series of money scandals surrounding a former aide.