Japanese Trade and Industry Minister Yuko Obuchi has resigned amid claims of the misuse of political funds, in a major blow for PM Shinzo Abe.
Yuko Obuchi is alleged to have used funds from her political support groups and other donations on make-up and other items unconnected to politics.
She handed Mr Abe a letter of resignation during a 30-minute meeting.
Correspondents say it is a setback to Mr Abe, who wants to bring more women into the top levels of government.
Ms Obuchi, 40, was one of five women appointed by Mr Abe in his last cabinet reshuffle last month and tipped by some as a future prime minister.
But last week came news that her staff had spent tens of thousands of dollars of campaign funds shopping for designer goods, and tens of thousands more on taking constituents on trips to Tokyo.
At a televised press conference on Monday, Ms Obuchi bowed in apology and said she was resigning because "we cannot let economic policy and energy policy stagnate... because of my problems".
"I take seriously the impact I have caused," she said. She also apologised for being unable to contribute to key goals set by Mr Abe, including economic recovery and "a society where women shine".
Local media, quoting unnamed sources, say another female cabinet member, Justice Minister Midori Matsushima, is due to resign as well.
Ms Matsushima had distributed paper fans carrying her image and policies at a festival in her constituency, said NHK, in a violation of election law.
The opposition Democratic Party filed a criminal complaint against her on Friday, and demanded her resignation.
The BBC's Japan correspondent Rupert Wingfield-Hayes says that this is not the end of Mr Abe's problems concerning his new female ministers.
Eriko Yamatani, minister in charge of the North Korean abduction issue, was shown in photographs with members of an ultra-nationalist group accused of hate speech against Japan's ethnic Korean community.
Mr Abe's first term as prime minister in 2006-2007 saw a string of scandals amongst his ministers, eventually leading to his own resignation for health reasons after just one year in office.