One in five unemployed parents who wanted to work cited lack of affordable childcare as a barrier, the Child Poverty Action Group charity says.
Low and middle-income parents who were surveyed also said that they could not find childcare for the hours they needed.
Half of those who were in work and had an annual household income below £30,000 said they did not have enough money to support their families.
Those returning to work after having a child were said to "hit a brick wall," as they struggled to retain their previous level of pay and job grade when most wanted permanent jobs with a "sense of purpose."
The charity's chief executive Alison Garnham said: "The Chancellor can help in this month's Budget. A good first step would be to pause and fix universal credit and restore its ability to make work pay for families."
Single parent charity Gingerbread carried out research which revealed there were a lack of suitable jobs for lone parents available. It called on the government to halt its harsh sanctions of lone parents who are claiming universal credit and are unable to find work.
Policy officer Laura Dewar called on the government to extend its free 30-hour per week childcare offer — currently it is only for those who work 16 hours a week or more.
She said: "The government needs to do more to promote work opportunities, and publicise help with childcare," adding that there was also a lack of awareness among parents about training opportunities that exist for those on universal credit.