Women are often forced to choose between flexibility and job security in a bid to meet their caring responsibilities, making them "dispensable", the Fawcett Society's chief executive said.
Speaking to the PA news agency, Sam Smethers said: "If you look back at the last 20 years the big increases in labour market participation have been amongst mothers and single parents in particular.
"What we are seeing now is that that trend is reversed, so unless we correct that, unless we get it back on track, we will literally have a significant step backwards."
Research by PwC published last month found 78% of those who have already lost their jobs as a result of the virus are women.
"Women are over-represented in low-paid work and precarious work," Ms Smethers said.
"They're people who are very 'dispensable' or otherwise easy to get rid of because they are on zero hours or minimum hours contracts."
The Fawcett Society also fears the collapse in childcare infrastructure - with more than 10,000 providers expected to go bust due to Covid-19 - could also force some mothers out of the workforce.
Campaigners are now calling for the Government to ensure experts in gender and health crises are involved in the process of rebooting the economy in the wake of the shutdown.
Dr Sophie Harman, professor of International Politics at Queen Mary's University, said the pandemic could prove "catastrophic" for women in Britain.
"It is sometimes during emergencies that the most egregious discriminatory practices happen because you can't spot them," she said.
"They are justified under 'well, we were just moving quickly' and so that's my concern of the wider ripple effect (of the pandemic)."