Mothers are leaving work because they don't want to behave like men, according to a study.
Ahead of International Women's Day 2014 tomorrow, researchers from the University of Leicester have revealed the masculine culture of the workplace.
Mothers in professional and managerial jobs are expected to stay late or get in early even if they have negotiated reduced working hours, according to the research.
It was also revealed they were expected to socialise with colleagues or clients in the evenings, although this could clash with their childcare responsibilities. They must do so because working culture is still organised by men, who are less involved in childcare.
In response to this, many mothers have left their jobs.
The paper was written by Emma Cahusac, series producer of BBC Television's The Culture Show and an organisational psychologist specialising in problems faced by organisations. Cahusac co-wrote the paper with Shireen Kanji, a senior lecturer at the University of Leicester School of Management.
The paper says: "Unless mothers mimic successful men, they do not look the part for success in organisations."
Many of the interviewed women found it hard to combine work and motherhood because of the dominant culture of presenteeism. This is the notion that they should be at their desks until late, even if there was nothing to do.
Susan, an ex-banker, said: "I would be in work by eight, but I would have to leave by six and actually I could do the job perfectly well."
However, Susan says was subjected to "barbed comments" from a woman who did not have children, over her early departure.
The researchers found that before they had children themselves, women not only accepted but encouraged the masculine culture of the workplace.
The mothers interviewed also needed to hide the fact that they were parents - imitating a masculine trait.
Nadia, a lawyer, told researchers: "The male partners never talked about their families. They've been very adept at keeping that separation between work and home."
In particular, mothers had to hide the fact that they were taking time off to look after sick children. One mother with a senior position at a charity, said: "You definitely would have to say you were sick, not the kid was sick."
The findings are presented in a research paper, Giving up: How Gendered Organisational Cultures Push Mothers Out, which has been published in the journal Gender, Work and Organisation.
The researchers interviewed 26 mothers based in London who had quit their jobs while pregnant, or following their return to work, but before their first child reached school age. The participants had been in professional and managerial jobs.
Of the women, 21 quit their jobs voluntarily, often because they had been sidelined after returning to the office. For example, Susan moved within her bank to lower-status project work after she had her first child.
Kanji said: "Many women leave high-powered jobs because they are relegated to lesser roles and feel the need to suppress their identities as mothers. This is not only unfair. As an economy, we cannot afford to waste such skilled and educated workers."