A Japanese government spokesperson has disclosed that he had received a "letter of support" from an affiliate of the controversial religious group previously known as the Unification Church.

Deputy Chief Cabinet Secretary Kihara Seiji told a Lower House committee on Friday that he had received the document in connection with last year's general election. He said he learned of its existence when he checked a list of around 1,000 recommendation letters that he'd received in four past elections.

Kihara said the affiliate of the former Unification Church had given him the document at its own volition, rather than him asking the group to do so. He offered an apology, saying he and his office lacked awareness about the religious organization.

Kihara was asked if he had signed a document expressing approval of the affiliate's policy proposals in return for its backing. He said he has thoroughly checked documents kept at his office and questioned his staff, but could not confirm such a fact.

The religious organization is under close scrutiny for its alleged shady marketing practices and for soliciting large donations from followers. Numerous politicians have acknowledged having contacts with the group.