A secretary of Upper House lawmaker Anri Kawai, who is the wife of a former justice minister, has admitted knowing that payments made to campaign staff during last year's Upper House election were illegal, sources close to the matter said Sunday.

The election campaign office of Kawai, who won a seat for the Liberal Democratic Party in July's House of Councilors election, is suspected of covering up payments to staff that were double the amount permitted under the election law.

The state-paid aide has told Hiroshima prosecutors during voluntary questioning that he was involved in providing daily allowances totaling ¥30,000 to a group of "election warblers," which refers to women who are driven around in small vans to tout their candidates over loudspeakers, according to the sources.