The shift includes tens of thousands of women educated to degree level.
The Fawcett Society said that since 2008, female “under-employment” in the UK has nearly doubled, to 789,000, and an additional 371,000 women have moved into self-employment, which is typically very low paid.
One in eight low-paid women now describes themselves as on a zero-hours contract, said the campaign group.
Its survey of 1,000 low-paid women found that almost half felt worse off than five years ago and nearly one in ten had taken out a loan from a pay day lender in the past year.
The Fawcett Society said increasing levels of women in low-paid work, along with the declining value of low pay, was contributing to a widening inequality gap between women and men, pointing out that last year the gender pay gap increased for the first time in five years and now stands at 19.1 per cent for all employees.
A high number of low-paid women are working significantly below their skill or qualification level, said the report, with over a fifth of those polled educated to degree level, while over a third described themselves as overqualified and over-skilled for their current job.
Dr Eva Neitzert, deputy chief executive at the Fawcett Society, said: “The evidence is clear, after five years of decline, the UK economy is back on the upswing.
“Employment is up, unemployment is down and GDP is improving. However, low-paid women are being firmly shut out of the recovery.
“The numbers of women in low paid, insecure work are still alarmingly high. Since the crisis in 2008 we have seen a nearly two-fold increase in the numbers of women working in insecure, part-time and temporary jobs where they would prefer to be in secure, full-time roles.
In addition, 371,000 more women have moved into self-employment – a form of work which is typically very low paid and where women earn an average of 40 per cent less than men.
“Since 2008 almost a million extra women have moved into types of work that are typically low paid and insecure.
“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 makes ends meet.
“Even the planned increase to the national minimum wage this October will only increase the value of the wage to 2005 levels in real terms. It is clear that work is not providing a sufficient route out of poverty for low-paid women.”
Dr Neitzert said it was “shocking” that over one in five women earning less than £7.44 per hour are educated to degree level, adding that low-paid women were seeing their position deteriorate despite the recovery.
Minister for Women and Equalities Nicky Morgan said: “We’re committed to delivering a long-term economic plan that works for women. We’re seeing more women in full-time work than ever before.”