Nurseries and childminders will be allowed to look after more children under Government plans to help parents battling soaring fees.
Staff will be able to take charge of six two-year-olds rather than four, and the ratio for under-ones will go up from three to four.
Under the new plans, a childminder would also be able to look after two babies instead of one and four under-fives rather than three.
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Education minister Liz Truss outlined the changes, which are part of reforms requiring carers of pre-schoolers to have higher qualifications.
She argued that they would make childcare more available as well as improving its quality, suggesting this would help to drive down prices.
But critics branded the reforms a "recipe for disaster" which could put children at risk and cast doubt on the prospect of cheaper care.
One parent writing on Mumsnet said: "How can this possibly improve childcare standards? Common sense says more children, less attention per child no matter how qualified the staff."
Another added: "I fail to see how someone can care for four young babies adequately. I do fear it will lead to accidents or even worse, simply because nobody has that many eyes in their head."
Britain families currently spend an average of 27% of their income on childcare - the second highest proportion in the world.
Despite this, the quality of care provided in the UK is said to be behind other European countries.
Ms Truss told an event at the Policy Exchange think-tank that the Government wants to bring in graduate-level Early Years teachers.
An Early Years Educator qualification will also be created, requiring practical experience and at least a C grade in English and maths GCSE.
The minister declared that nursery staff had to be paid more to improve the system, citing an average wage of £6.60 an hour.
Easing rules on ratios will give nurseries the "headroom to pay higher salaries", Ms Truss said.
"We have learned from other countries that deliver better value and better-quality childcare. We have looked across Europe and beyond ...
"I have been particularly struck by the high status and trust afforded to childcare professionals in continental Europe."
She added: "Other European countries have taken a different approach on ratios. They think that the quality of staff is the most important thing.
"Whereas in England nursery staff may look after no more than three one-year-olds, in France they can be responsible for five - and there are no limits in Denmark, Germany or Sweden.
"That is why we are encouraging nurseries to use their professional judgment and enjoy greater flexibility."
Anne Longfield, the chief executive of families charity 4Children, said the proposals could "transform the early years profession in this country" and they were also welcomed by Ofsted.
But Neil Leitch, chief executive of the Pre-School Learning Alliance said: "We are absolutely appalled by this fixation to alter ratios ... This is a recipe for disaster."
TUC general secretary Frances O'Grady said the changes would "not reduce costs and instead risks reducing the quality of care".
Chris Keates, from the NASUWT teachers' union, warned that sacrificing appropriate ratios to secure higher pay levels and more qualified staff was a "flawed strategy".
"It is more likely that any increased revenues gained by reducing ratios will simply be diverted to increasing profit margins rather than to enhancing the pay and conditions of staff and the quality of provision for children," he said.
Shadow education secretary Stephen Twigg said: "This Government has created an affordability crisis by cutting support and pushing up costs for parents.
"Watering down quality is the wrong way to try to deal with the problem they've caused. Experts are warning this could threaten child safety and won't reduce costs. Parents will be worried.
"With a £1,700 toddler tax for families with two children, and 401 fewer children's centres, parents are being locked into inflation-busting cost rises while the quality of childcare is undermined."