Prime Minister Shinzo Abe on Monday rejected opposition calls to launch another search for a leaked internal document that suggests he used his clout to help a longtime confidant open a new veterinary medicine department at his university.

Abe's refusal came after the main opposition Democratic Party on Friday released copies of an email message that showed the document in question being sent to eight senior education ministry officials as an attachment.

The leak of the email, dated Sept. 27, has given the opposition fresh ammunition to demand that the government launch another search. The government previously denied the authenticity of the document, citing its unknown origin.