Mothers surveyed were 23% more likely than fathers to have lost their jobs temporarily or permanently during the crisis.
Of those parents who were in paid work prior to the lockdown, mothers were 47% more likely than fathers to have permanently lost their job or quit. They were also 14% more likely to be among the UK’s 8.4 million furloughed workers.
As a result, mothers are now nine percentage points less likely to still be in paid work than fathers.
The IFS warned that this reduction and interruption of mothers’ working hours may harm women’s careers in the long run and further increase the gender pay gap.
Before the coronavirus crisis, working mothers did paid work for 6.3 hours on an average weekday, this is now 4.9 hours. In comparison, working fathers’ hours have fallen from 8.6 hours to 7.2 hours.
Childcare is also affecting working hours, with almost half (47%) of mothers' paid work hours split between work and various activities such as childcare. This was compared with just 30% of fathers’ paid working hours.
Mothers reported looking after children for an average of 10.3 hours per day, 2.3 hours more than fathers and were doing housework for 1.7 more hours than fathers.
HR consultant Guy Pink HR said despite the figures, mothers' juggling abilities should be a draw for businesses.
He said: “When recruiting we need to value the role of houseworkers juggling multiple roles and ask why organisations do not value someone able to juggle a full-time role, homeschooling and running a house over someone that cannot multitask?
“Lockdown will not go on indefinitely - it cannot, because as a country we cannot afford it - but when our staff return to the workplace I am sure that flexible working will be high up on the agenda for both sexes, and organisations need to be able to support this newer way of working.”
IFS’s study showed that in families where the father has lost his job while the mother had kept hers, men and women split housework and childcare responsibilities fairly equally.
Yet in situations where the mother had stopped working for pay while the father continued, she did twice as much childcare and housework as her partner.
Lucy Kraftman, research economist at IFS, said this inequality is bound to have a long-term impact.
"Mothers are doing, on average, more childcare and more housework than fathers who have the same work arrangements, be that not working, working from home or working outside the home,” she said.
“The vast increase in the amount of childcare that mothers are doing under lockdown, which many are juggling alongside paid work, is likely to put a strain on their wellbeing.”
However, IFS’s research showed that fathers are on average doing childcare for eight hours each day, twice as many as in 2014-2015. This suggests they are taking on more household responsibilities than they were pre-crisis.
Sonya Krutikova, deputy research director at IFS, saw reason for hope in this finding.
She said: "This may bring about changes in the attitudes of fathers, mothers, children and employers about the role of fathers in meeting family needs for childcare and domestic work during the working week.
“It may serve as an impetus for a more equal sharing of childcare and housework between mothers and fathers after lockdown ends."
Pink added that the situation was an opportunity for HR to reevaluate the way parents work.
He said: “HR cannot change societal views but they can help to alter the way we do work.
“The best way HR can support working parents is by evaluating the benefits that are in place - do they support working parents such as childcare vouchers vs gym membership for example.
“By training managers and supervisors to be able to offer support and understanding to working parents throughout lockdown and beyond. A return to school for kids will be a major step forward to helping, so I think this will become less of an issue come September.”
IFS and the UCL Institute of Education surveyed 3,500 families with two opposite-gender parents between 29 April and 15 May on how they were sharing work and domestic responsibilities.