As of today, working parents in England will be entitled to 30 hours of free childcare for three- and four-year-olds, up from the previous 15 hours.
However, a Department for Education-commissioned evaluation of four early rollout areas, where extended provision has been available since April, found that 12 per cent of providers are not taking part and do not plan to do so. Of those that did not plan to offer 30 hours of free childcare, around half cited a lack of funding as the reason.
Other barriers to taking part raised by providers not intending to offer 30 hours include a shortage of space and a lack of staff.
A further 10 per cent of providers in the four early rollout areas - Tower Hamlets, Dorset, North Yorkshire and Leicestershire - said they plan to offer 30 hours but are not currently doing so as they are waiting for spaces to become available or because they need more time to adjust.
Meanwhile, six per cent of providers in these four areas said they intend to offer the new entitlement but are not currently providing any places.
Of providers in the early rollout areas that did take part, 39 per cent said their profits had decreased, compared with 24 per cent that said they had increased.
The study echoes the findings of a separate DfE evaluation, published in July, into provision in eight "early implementer" council areas, which began piloting the 30-hour offer in September 2016.
The early implementer councils were initially expected to provide 30 hours places without any additional funding from central government, although the Department for Education did eventually provide some extra money for providers following talks. The early rollout areas received the final funding rate, that all providers will receive as of today - a minimum of £4.30 an hour.
That early implementer evaluation found that 48 per cent of private providers offering the 30-hour entitlement suffered a drop in profits.
"Just like the early implementer pilot, childcare providers taking part in the early rollout of the 30 hour offer reported higher costs and lower profits," Neil Leitch, chief executive of the Pre-school Learning Alliance, said.
"Is it any surprise, then, that a significant proportion of providers in the four early rollout areas chose simply not to deliver the extended hours?
"The government has the ability to make this a success, but its constant refusal to listen to any criticism about what is clearly an incredibly flawed policy, and to acknowledge that the scheme simply cannot succeed in the long term without a significant increase in funding, is doing just the opposite."
National Day Nurseries Association chief executive Purnima Tanuku said the government must acknowledge that there is a serious problem and that we are at a crisis point with 30 hours funded childcare.
"It must be acknowledged that there is a funding shortfall to pay for this childcare, which is not free and never has been."
But despite the concerns around funding, this latest DfE evaluation concludes that "there is no specific reason to believe that 30 hours free childcare will not be a success".
"A high proportion of providers were willing and able to offer extended hours places and there was no evidence that financial implications were a substantial barrier to the delivery of the extended hours," the evaluation states.
A survey published yesterday by the Pre-school Learning Alliance found that half of early years providers plan to increase or introduce extra charges to parents to recoup the cost of offering 30 hours of free childcare.
Education Secretary Justine Greening said: "High-quality childcare not only helps our children get the best start in life, it supports many parents who want or need to work.
"For too long lots of families really struggled to manage the cost of childcare and that's why we have delivered on our promise to provide 30 hours free - saving working families around £5,000 a year.
"Alongside the support we are giving through tax-free childcare and Universal Credit, it will make a real difference to families' lives."