The Government is being warned about a potential childcare crisis unless the sector receives an emergency bailout.
Childcare provision, including nurseries, childminders and holiday schemes, is vital to economic recovery, so parents can go back to work, said the TUC.
The union organisation called for an emergency government cash boost, similar to the financial help given to transport networks.
Some nurseries could cut their hours or have fewer places, while at least one in four may struggle to reopen after the lockdown ends, said the TUC.
It warned that if the childcare suddenly becomes unavailable, many parents could lose their jobs or pay, as they struggle to balance work and care.
TUC general secretary Frances O'Grady said: "Our childcare sector is on the brink of collapse, and it's putting women's jobs on the line.
"If childcare places disappear, women will be pushed out of the workforce.
"Women workers are bearing the brunt of this crisis, both on the frontline and at home. Mums have picked up the majority of childcare while nurseries and schools have been closed, and many have had to sacrifice work hours and pay to do so.
"The Government can't stand by while mums are forced out of their jobs. Childcare is necessary if we are going to work our way out of this economic crisis and stop the misery of mass unemployment.
"If we're all in this together, nurseries desperately need Government cash to stay open."
National Day Nurseries Association chief executive Purnima Tanuku said only 35 per cent of children have returned to nurseries this week in England.
She said: "This loss of parental income means that 71 per cent are expecting to operate at a loss for the foreseeable future.
"Following on from years of Government underfunding for childcare places, many childcare businesses fear for their future, with four per cent admitting they will have to close unless they are given further financial support.
"Any closures will have a huge impact on the local economy and put more experienced, dedicated practitioners out of work, 98 per cent of whom are women."
