It found that only one in five (22%) fathers now have IP with two-thirds (64%) having life cover and less than a third (30%) critical illness (CI).
The provider warned that this low take up could leave families vulnerable if a dad died or became seriously ill.
Its study suggested that fathers did £21,306 worth of work around the home each year, averaging 50 hours a week on housework and child care, although this figure has dropped from 53 hours in 2009.
On average, 20 of those 50 hours are spent on childcare, 6.5 on shopping and household tasks, 7 on cleaning and 5.5 on cooking.
When asked how couples thought their partner would manage in the event of their death, the most popular response (42%) was to rely on grandparents to look after the children, with 31% saying they would work part-time.
L&G said this would have a significant impact on the overall household earnings and standard of living, and further noted that only 34% of parents have made a will.
Bonnie Burns, product development director for Legal & General, was concerned about the results and feared people were wrongly assuming the state would support them if the worst happened.
“How would we cope with all the domestic work and childcare that Dad does, if he suffered a critical illness or died?” she said.
“People shouldn’t assume that extended family or the State will fill the gap. Given the current economic uncertainty, buying these products can help provide peace of mind for a family and help maintain its living standards if Dad was critically ill or died.
“With the purchase of protection products so low, this could leave some families exposed and at risk of suffering financial hardship in the event of a father’s death or critical illness,” she added.
