Working mothers are happier than stay-at-home mums no matter how many hours they have to spend in the office, according to academic research.

Even mothers who work more than 45 hours a week enjoy much higher levels of “life satisfaction” than full-time mums, the study by the Institute for Social and Economic Research at the University of Essex found.

The findings challenge the assumption that thousands of mothers would be happier if they stayed at home with their children.

Research conducted by the Centre for Policy Studies three years ago concluded that almost half of working mothers have jobs purely because they need the money.

The research also casts doubt on the popularity of David Cameron’s promise to offer tax breaks to married couples to help mothers stay at home.

Although the report, entitled Job Satisfaction and Family Happiness, found high levels of life satisfaction among women who work part time, those who work 30-34 hours a week and 41-45 hours a week also reported high levels of wellbeing.

“Women without children do not care about their working hours, while women with children are significantly happier if they have a job, regardless of how many hours it entails,” Alison Booth and Jan Van Ours, the authors of the report said.

The report used data compiled in eight years of the British Household Panel Survey, which questions 5,500 households on an annual basis. The researchers also discovered that children in a household bring no increase in life satisfaction for men. Among women, it increases only when children start going to school.

“Given this finding, perhaps it is not surprising fertility is declining in Britain,” the report concludes. The Conservatives will outline plans today to make single parents, who have children at school, work and to make joining a training programme a condition of receiving benefit.

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