Analysis by the union organisation to mark the 50th anniversary on Friday suggested women are more likely than men to be key workers and so be on low pay.
Of an estimated 9.8 million key workers, nearly two-thirds are women, while 2.6 million female key workers earn less than £10 an hour, said the TUC.
TUC general secretary Frances O'Grady said: "Fifty years after brave women won the legal right to equal pay, coronavirus has confirmed that pay inequality is still rife in Britain today.
"Working women have led the fight against coronavirus, but millions of them are stuck in low-paid and insecure jobs.
"As we emerge from this crisis, we need a reckoning on how we value and reward women's work. Without proper change it will take decades to close the gender pay gap."
Separate TUC analysis of official data shows that at current rates of progress it will take around 50 years to achieve pay parity between men and women.
Joe Levenson of the Young Women's Trust said: "Even before the coronavirus crisis began, young women were locked out from accessing equal pay and opportunities in the workplace.
"Young women are amongst the hardest hit by the financial and domestic impact of coronavirus as they are pushed back to caring roles, reduced hours and will return to work at the mercy of their employers' discretion."
Minister for Women and Equalities, Liz Truss, said: "The work of those women whose drive and determination led to the Equal Pay Act has not been forgotten. And, as we celebrate today, we are determined to continue their legacy.
"We should use this time to push forward better, and more modern ways of working and flexibility in our jobs.
"As our country recovers from this unprecedented global crisis and we rebuild our economy, we must rebuild it so it works for everyone."