Earning less than the living wage is the "norm" for women working part-time in many parts of Britain, according to a new study.
The TUC said most part-time women workers in more than 50 local authority areas were on less than the living wage, including three out of four in West Lancashire and two-thirds in West Somerset.
The union organisation called on employers to tackle the issue, adding that the Government could lead by example by making sure firms winning contracts paid their staff the living wage – currently set at £7.65 and hour and £8.80 in London, compared with the national minimum wage of £6.31.
TUC general secretary Frances O'Grady said: "Women are bearing the brunt of growing in-work poverty across Britain today.
"The living wage was created so that work can provide staff with a basic standard of living, but in many parts of Britain, most women working part-time are way off earning this. Women of all ages and skill levels often find themselves trapped in low paid jobs. Women would gain most from a greater take-up of the living wage by employers," she added.