Save the Children and Daycare Trust rue childcare costs
Childcare costs have risen every year for 10 years leading to some parents being "priced out of work", charities claim.
Save the Children and the Daycare Trust are conducting an investigation into how the costs are affecting families everyday lives.
Costs have risen to £177 a week for a 50-hour nursery position for a child aged under two, the Daycare Trust said.
Costs are among the highest in the world, the charities say.
"Childcare is so expensive it is becoming a luxury that only families earning a very good wage can comfortably afford," said Sally Copley, head of UK policy at Save the Children.
"For families on low incomes, they simply will not earn enough to cover their childcare bill - effectively pricing the poorest families out of work."
Anand Shukla, acting chief executive of the Daycare Trust, said: "Our research shows that childcare costs have risen every year for the last 10 years.
"We know that childcare is expensive, but we need to know how much of a barrier it is to parents being able to find or keep a job."
Changes that came into force in April mean that tax relief for employer-supported childcare is no longer available to new claimants who are high-earners.