No families will miss out on an expanded free childcare system despite challenges in the rollout, the government has insisted.
Reports suggest plans to provide 15 hours per week free childcare to some working parents from April are at risk due to technical glitches and delays.
On Monday, the government announced it would write to parents with a workaround for a known IT issue.
But campaigners said the government is "in total denial" over the problem.
From April, working parents of two-year-olds will get 15 hours per week during term time, with children from nine months included from September.
Working parents of children under five will be entitled to 30 hours' free childcare per week when the scheme is fully rolled out from September 2025.
But parents have been warned they may be unable to access the first year of government's flagship scheme because of problems with the rollout, first reported in The Times newspaper.
Education campaign group, the Early Years Alliance (EYA), said many nurseries, pre-schools and childminders have been left with "no idea what funding rate they will receive from April, making it impossible to plan".
In some cases, this has meant childcare providers have been unable to accept applications via the scheme, the EYA said.
Neil Leitch, CEO of the EYA said: "Add to this the fact that many providers are still battling the impact of years of underfunding, and that we are in midst of the worst early years recruitment and retention crisis in recent memory, and there is no doubt that our sector is in crisis.
"To argue otherwise suggests that the government is in total denial over the scale of the challenge it is facing."
Labour accused the government of "bungling" a key pledge, which is now "in tatters".
"Funded hours are no good if families can't access them," shadow education secretary Bridget Philipson said.
Labour have trailed plans to boost childcare with thousands of new nursery places in primary schools, commissioning former head of Ofsted Sir David Bell to help find new ways to increase levels of childcare provision.
No 'missing out'
Prime Minister Rishi Sunak admitted "there are some practical issues that certain families are facing".
Mr Sunak pledged the issues would be resolved and "all of those families will get the childcare that they are eligible for".
He said the government will "work through these issues to make sure everybody gets the support that they need".
The Department for Education (DfE) said it had fixed an IT issue that left some parents unable to access codes needed to secure a place with a childcare provider in time. Childcare Minister David Johnston said the government will write to all affected families with a code.
When asked how many families would miss out on access to the scheme because of technical issues, Mr Johnston said: "None".
Mr Johnston said: "No parent should worry they will lose out.
"We want parents to be able to access the new offers as soon as they can."
The DfE expects the new scheme, announced in the 2023 spring budget, will cost an estimated £4.1bn extra a year by 2027-28 - increasing the departments total annual spending on childcare to £8bn.
OceanNewsUK analysis estimates that demand for childcare places is likely to have risen by about 15% by the time the expansion is in place. This is equivalent to more than 100,000 additional children requiring full-time care.
Childcare places in England fell by 1% in 2023, mainly because of childminders leaving the sector, but the government says the population of pre-school children is also decreasing.
