Men 'no longer main breadwinners'
The GMB said its research revealed that equal pay now directly impacted on the economic prosperity of regions, as well as being an issue of fairness.
The union's report showed that in 210 out of 374 local authority areas in England, Wales and Northern Ireland, women made up at least half of all employees.
Northern Ireland had the highest proportion of women workers at 52%, followed by Wales, the North West and the North East, all with just over half.
Paul Kenny, the GMB's general secretary, said: "These figures show that for workers resident in most areas in England, Wales and Northern Ireland there are more women in employment than there are men in employment.
"That means that equal pay for women is not just an issue of fairness but is something that directly impacts on the economic prosperity of many areas.
"Politicians should no longer think of men as the breadwinner. They should consider the impact on women's wage packets and their experiences at work when they propose changes to employment policies.
"Employers need to acknowledge the fundamental importance of flexible working and family friendly policies as women still continue to take on the burden of domestic work and childcare."
© 2012 Press Association