But he said Mr Akagi might have to explain himself further to dispel allegations of impropriety.

Mr Akagi was only appointed in June, after his predecessor killed himself.

Two other of Mr Abe's ministers have resigned since he became prime minister 10 months ago.

Japan's Kyodo news agency reported that Mr Akagi claimed millions of yen in expenses for an office based at his parents' home registered to a political group supporting him.

However, Mr Akagi's father told Kyodo that the home had never been used as a political office.

Mr Akagi has denied doing anything illegal, a stance which was backed up by Mr Abe.

"There is nothing wrong with it," the prime minister told a TV interviewer, adding that "many lawmakers are doing the same thing".