Retired women effectively go more than four months every year without getting a pension because of a gender gap, according to research.
The TUC estimated women were losing the equivalent of £7,600 a year on average.
The union organisation said compared to men, retired women effectively stop receiving pension income from today.
The income gap between men and women in retirement is now 36.5%, according to research from the Prospect union.
The Government has revived the Pension Commission, which will bring together unions, employer and independent experts to look into the causes of the gap.
TUC general secretary Paul Nowak said: “Everyone deserves dignity and security in retirement, but too many retired women have been left without enough to get by.
“We must make sure that these inequalities are addressed for future generations.
“That’s why reviving the Pensions Commission – bringing together unions, employers and independent experts – is a vital step forward.
“We now have a chance to make sure everyone, including women, receive the decent retirement income that all workers need.”
A Government spokesperson said: “We’re determined to close the gender pensions gap, and the new state pension has already reduced historic inequalities faced by women and low earners.
“Alongside this, the Pensions Commission will tackle barriers to close the gender pensions gap in private pensions to ensure women have the dignity and security they deserve in retirement.”
