Japan’s prime minister, Shinzō Abe, has appointed just one woman to his new cabinet, raising questions about his commitment to “make women shine” in business and public life.

But he claimed that the regional revitalisation minister, Satsuki Katayama, had “the presence of two or three women”.

Deepening the controversy over gender equality in Japan, Katayama was forced to buy a new dress after being told her outfits did not comply with the existing official dress code.

Abe was accused of repaying party factional debts rather than addressing the gender imbalance in politics following his reshuffle on Tuesday, a fortnight after he was re-elected president of the ruling Liberal Democratic party (LDP).

His victory virtually guarantees he will still be in office in November next year, making him the country’s longest-serving prime minister.

But his decision to appoint one woman to the relatively low-profile role of regional revitalisation minister prompted criticism from an outgoing female minister and uncomfortable questions at his post-reshuffle press conference.

Japan’s new regional revitalisation minister, Satsuki Katayama, at a news conference in Tokyo. Photograph: Issei Kato/Reuters

Asked why there was only one woman in his 19-member cabinet – one fewer than in his previous lineup – Abe claimed he had only just embarked on his “womenomics” campaign to raise the standing of women in the workplace, although it is a cause he first championed soon after becoming prime minister in late 2012.

“We must recognise that the ratio of women cabinet ministers is low compared with other countries, but Japan has just begun to create a society where women can be more active,” he said. “I think we will nurture people who can become cabinet ministers.”

He claimed that the lone female appointee, the former career bureaucrat Katayama, had the determination of multiple women. “She is incredibly feisty. I know there is only one woman in this cabinet, but Ms Katayama has the presence of two or three women. I hope she will use that to promote the goal of female empowerment,” he said, according to the Japan Times.

Seiko Noda, who was replaced as internal affairs minister by a man, said she was “extremely worried” about the lack of female representation in senior positions in the party.

Katayama, whose brief includes promoting gender equality, was forced to buy a new dress shortly before a ceremony at the Imperial Palace to announce the new ministers, after a Cabinet Office official said neither of her two existing outfits met the dress code.

The Mainichi newspaper said cabinet officials told her other outfits were inappropriate because the jackets and dresses were different colours, adding that a long dress and jacket of the same colour was “the norm” – reportedly suggesting silver.

Katayama and her secretary rushed to a department store and later returned to her office carrying a bag. “I found an outfit that follows the dress code,” she told reporters, according to Kyodo News. She wore a long silver dress with matching jacket in the official photos.

While the new cabinet includes 12 first-time appointees, Abe was accused of rewarding politicians who supported his LDP re-election campaign and who can be relied on to back his agenda, including plans to revise the country’s pacifist constitution.

“He has appointed old friends and reliable allies and kept people in key portfolios to buy stability,” said Jeffrey Kingston, the director of Asian studies at Temple University in Tokyo, adding that Katayama’s appointment “exposes the empty grandstanding on womenomics”.

The challenges facing women in the Japanese workplace received widespread attention this summer after it was revealed that Tokyo Medical University had deliberately altered entrance exam scores for more than a decade to restrict the number of female students and ensure more men became doctors.

Earlier this week, Yuka Ogata, a female local assembly member, claimed she was being targeted by male colleagues after taking her baby son into the chamber last year to highlight the difficulties encountered by working parents.

Ogata, whose experience generated negative headlines about Japan’s treatment of women in the workplace, was expelled from a session of the Kumamoto municipal assembly last week for sucking a cough sweet while addressing colleagues.

Japan ranked 114th out of 144 countries in the World Economic Forum’s global gender equality rankings last year – down three places from a year earlier and the lowest among the G7 nations. The report said the poor assessment reflected the low number of women in politics.

Only 10% of MPs in Japan’s lower house are women, according to the Inter-Parliamentary Union.