Fathers who spend more time caring for their babies alone are less likely to separate from their partners than those who are less hands-on, according to new research that suggests the government needs to do more to encourage paternity leave.

The study, which examined the link between domestic duties and partner relationships of more than 13,000 mixed-sex couples, found a direct correlation between involved fatherhood and long-term relationship stability, regardless of other variables such as ethnicity or wealth.

Fathers who took sole charge of babies before they turned one were as much as 40% less likely to subsequently break up with their partners, the research found.

“Our results show that relationships are less likely to break down over the long term if the dad looks after the baby on his own without the mother being there at least a few times a week during the first year,” Dr Helen Norman, the report’s lead author from the University of Manchester, said. “This correlation holds regardless of all other variables such as ethnicity, gender-role attitudes and household income.”

The research, which built on previous work in 2012, said it was impossible to pinpoint cause and effect. But Norman noted that academics have previously argued that solo paternal care has a positive effect on fathers’ happiness and the development of father-child relationships, which should make for happier father-mother relationships.

Norman, who has a six-month-old child, said that giving new mothers a break may be an important factor. “If I have a bit of time out I feel refreshed and happier when I come back. It also allows the mother to engage in paid work outside of the home and she can compete on a more equal footing with her partner,” she said.

Data shows that the number of men who take substantial time out for solo childcare remains small, with more than 80% of fathers still working full-time. The take-up of shared parental leave, whereby mothers can transfer some of their allowance to their partners, has been relatively low.

Surveys and studies show that during the crunch early years of their children’s lives, many men still felt financially, professionally and culturally unable to take time off or downshift. Men said it was hard to persuade employers to take their request for leave seriously, and expressed concerns about being sidelined if they asked for flexible working patterns.

Leading MPs called earlier this year for men to get 12 weeks of ring-fenced “use-it-or-lose-it” paternity leave to encourage fathers to spend more time with their infants.

Jo Swinson, deputy leader of the Liberal Democrats, who recently took her baby to a Commons debate, said the research made a lot of sense. Sharing care, as she does with her MP husband Duncan Hames, gave couples more in common, she said, adding that sole childcare was empowering for fathers. “For couples where care is shared, not only does that couple have more in common, which can enhance the relationship, but it becomes a shared endeavour, which helps reduce stress,” she said.

“Surveys have shown that men are happier and healthier if they are much more involved as fathers, so that would have a knock-on effect. And for women it will help them if they are doing paid employment,” she said.

Swinson is the architect of a private members bill seeking to require all companies with more than 250 staff to publish their parental pay and leave policies. Ten big firms have already signed up. Others, such as Aviva and the Telegraph newspapers, have already announced equality of paid parental leave for men and women.