The Changing Labour Market 2: Women, Low Pay and Gender Equality in the Emerging Recovery is based on a survey of 1,003 low-paid women and the latest ONS labour market figures.
It suggests the number of underemployed women is twice that of 2008. Additionally, 371,000 women have moved to self-employment. The research shows that self-employed women earn on average 40% less than their male counterparts.
The report also reveals that 25% of women earn less than the living wage (£7.44 outside of London) compared to 15% of men. One-fifth of these women (20%) hold a degree or equivalent qualification.
Fawcett Society deputy CEO Eva Neitzert said the report is evidence that women are being "shut out" of the economic recovery.
"Overall, since 2008 almost a million extra women have moved into types of work that are typically low paid and insecure," she said.
"We are concerned that at a time when the numbers of women on low pay are increasing, the value of their pay is declining in real terms, meaning they are struggling more than ever to make ends meet."
Minister for women and equalities Nicky Morgan insisted the government is looking to help women "make the right choices" in employment.
"We’re committed to delivering a long-term economic plan that works for women," she added.
"That’s why we are giving employees the right to request flexible working as well as introducing shared parental leave, and introducing tax-free childcare – also available for eligible parents who are self-employed."