The brain drain - which according to the research by the Education Policy Institute (EPI) risks harm to children's life chances - is being driven by falling childcare worker pay, while retail wages are on the rise.
Growing workforce instability has serious implications for the future of childcare provision, according to the EPI - concerns echoed by Neil Leitch, chief executive of the Early Years Alliance.
"You can't blame these dedicated professionals for swapping the pressure and long hours of the early years for more pay and less stress working in a supermarket," he said.
"This is the fault of government and, if ministers are serious about the early years, they need to accept the reasons behind why people are leaving the sector and start funding childcare properly."
The EPI compared pay, working conditions, demographics and qualifications of workers in the childcare and retail sectors in England, using quarterly data collected from the UK Labour Force Survey of 100,000 individuals.
It warns that on current trends, sector pay may be overtaken by retail worker pay by 2021.
Since 2013, childcare real wages have fallen from £8.59 to £8.19 per hour, while retail wages have increased in real terms from £7.34 to £7.75, the research suggests.
Some childcare workers are already paid less than those in retail, even when they are qualified to the same level - a Level 2-qualified childcare worker now earns 22 pence less per hour than their retail counterparts.
Around one in four of former childcare workers cites "unsatisfactory pay" as the main reason for leaving the sector.
Report author Avinash Akhal said: "These trends ought to alarm policy-makers. With high-quality childcare playing a vital role in the early years of a child's life, it is critical that there is a good supply of well-qualified workers.
"Failure to resolve recruitment problems could impact the provision of childcare and early years education, heightening the chance of development gaps between disadvantaged pupils and their peers widening."
Leitch added: "Childcare professionals do vital work and deserve higher pay. There's no one that disagrees with that - the problem is that the government isn't prepared to foot the bill.
"Most childcare providers tell us they're struggling to break-even, many are making a loss and I hear every week from those who have been forced to close because of underfunding. It's no wonder childcare professionals are underpaid if that's the climate in the sector: there simply isn't enough money.
"This all boils down to the type of childcare we want to see in this country. Do we want a high-quality early years sector, delivering safe care and setting up our youngest children for a lifelong love of learning?
"Or do we want a race to the bottom where children come second to financial sustainability? It's clear where we will end up if things don't change soon."
Stella Ziolkowski, director of quality and training at National Day Nurseries Association (NDNA), said the new research echoes its own findings, including that almost twice as many childcare workers are claiming benefits as those in other sectors.
"This research clearly demonstrates an inability for employers to increase salaries," added Ziolkowski.
"Childcare providers want to pay staff well and reward their skills and experience but as these figures show, they are less and less able to compete in the labour market.
"In some instances this is causing business failure and nursery closures.
"These findings represent a real failure of the Government's workforce strategy. The strategy is not supporting continuity of care for children, or fostering a high quality, happy and engaged workforce which is needed to achieve the best outcomes for children."