Hard-working fathers in the UK are cutting their long hours, while mothers are working more, researchers say.
Men with a partner and children at home work longer hours than other working men, but their hours have fallen in the past 10 years, they say.
Three in 10 men in this family set-up work 48 hours a week, research by NatCen Social Research and University of East Anglia suggests.
And one in 10 such fathers works more than 60 hours each week.
The Fathers and Work research was based on the long-term EU Labour Force Survey.
It specifically studied fathers in this type of family unit, rather than those men who were separated from the mother of their children, and found that higher proportions of them were working long hours when compared with women and all other men - especially those without dependent children.
Decrease in weekend working
However, the figures suggest that fewer of these fathers were taking on such workloads than in previous years.
In 2001, 40% of them worked 48 hours or more a week, while 13% worked 60 hours or more.
By 2011, 31% worked more than 48 hours, while 10% worked for more than 60 hours.
The researchers also say there has been a significant fall in the proportion of fathers working evenings, nights or weekends.
About half never work evenings, compared with 33% in 2001, while three-quarters never work nights - up from 66%.
On average, they say the usual weekly working hours of fathers in two-parent households who work full-time fell from 47 to 45 hours a week, in line with a decrease among all men working full-time, whose hours dropped from 46 to 44 hours a week.
At the same time, mothers are increasingly sharing the responsibility for earning money, say the academics.
Mothers who live with their partner and children are more likely to be in full-time work than they were a decade ago. The proportion of households with two full-time earners has increased from 26% in 2001 to 29% in 2011.
And mothers who work part-time, with partners who work full-time, now work slightly longer hours, up from 17.7 to 18.2 hours per week on average.
Working hours of all women working full-time fell from an average of 41 hours a week in 2001 to 40 hours in 2011, the study suggests, while the average weekly working hours of mothers working full-time have remained stable at 39 hours a week.
Margaret O'Brien, professor of child and family studies at UEA, said: "Our research suggests that fathers are spending less time at work and mothers are spending more.
"There may be a number of reasons for these changes, but the combination of this means that fathers are now more likely to be at home with their children and free to take a greater role in family life."
The academics say that in Britain only one in five families has a father who is the sole earner.
The research is published at modernfatherhood.org.