The cost of childcare in London has shot up by 58% over the past nine years - but the average pay for parents with a one-year-old child has only increased by 8%.
The analysis, released by the Trades Union Congress (TUC), found the cost of childcare across the capital has risen more than seven times more than wages since 2008.
Other areas of the country have also been affected.
For example, in the East Midlands, childcare has also risen seven times faster than pay, and in the West Midlands it was five times faster, the Mirror reported .
While there is government support for childcare aged two and older, most working parents with one-year-olds do not get any state help, the union organisation said.
Parents are spending an increasing amount of their pay on childcare, the TUC added.
Single parents working full-time with a one-year-old in nursery for 21 hours a week spent more than a fifth of their wages on childcare last year, up from around a sixth in 2008.
Two parents working full-time have seen spending on childcare jump from 8% in 2008 to 11% last year, the study showed.
TUC general secretary Frances O'Grady said: "The cost of childcare is spiralling but wages aren't keeping pace.
"Parents are spending more and more of their salaries on childcare, and the picture is even worse for single parents.
"Nearly a million working parents with one-year-old kids have eye-watering childcare bills.
"There is a real gap in childcare support for one-year-olds until government assistance kicks in at age two.
"Parents need subsidised, affordable childcare from as soon as maternity leave finishes to enable them to continue working, and so mums don't continue to have to make that choice between having a family and a career."
Ellen Broome, chief executive at the Family and Childcare Trust, commented: "Childcare is as vital as the rails and roads to making our country run.
"It boosts children's outcomes, supports parents to work and provides our economy with a reliable workforce.
"For too many parents, however, high childcare costs mean that it does not pay to work.
"Low-income families claiming Universal Credit typically take home just £1.96 per hour after childcare costs have been paid, and some get even less than this.
"We must make sure every parent is better off working after childcare costs."
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