Ambassador to Australia Lee Jong-sup arrives at the foreign ministry building in Seoul to attend a meeting of six ambassadors on defense cooperation on Thursday. (Yonhap)

President Yoon Suk Yeol on Friday approved the resignation of Ambassador to Australia Lee Jong-sup amid mounting criticism of his appointment and departure that came despite the fact that he was subject to an investigation.

Lee offered his resignation earlier Friday, 25 days after he was appointed to the position, as he has been under intense scrutiny since he was named the ambassador in Canberra early this month, after revelations that he had been banned from leaving the country over the investigation into allegations that he interfered in an internal military probe into a Marine's death last year.

Critics have accused Lee of running away from the investigation and leaving the country to take up the job shortly after the exit ban on him was lifted.

Lee has denied any wrongdoing.

Lee returned home on March 21, 11 days after he assumed the job, to attend a defense cooperation meeting of South Korean ambassadors to six countries, including Australia. But questions arose that the meeting could have been organized to give Lee a pretext to come back home.

Lee plans to stay in Seoul to do all he can to "strongly respond to all procedures," according to Lee's lawyer, Kim Jae-hoon.

The lawyer said Lee repeatedly called for the anti-corruption investigation office to quickly summon him for questioning, but he still has not heard from the office.