Education Secretary Bridget Phillipson says the free childcare rollout "won't be the sunlit uplands promised by the Tories".
The education secretary has said the rollout of 30 hours' free childcare by 2025 "will go ahead" but some parents might not get their first choice of nursery or childminder.
Bridget Phillipson said that while all parents will be able to get the free 30 hours by September next year, they may not be able to get their first choice place.
This is down to a lack of available staff and places, Ms Phillipson said.
Writing in the Sun on Sunday, she said: "I'm not surprised parents feel cheated and let down.
"The last Conservative government recklessly rushed through a childcare pledge without a plan to carry it out, once again leaving Labour to pick up the pieces and fix the foundations."
She added: "Yes, the 2025 childcare rollout will go ahead - but it won't be the sunlit uplands promised by the Tories.
"That means in some parts of the country while parents may receive the hours they were promised, they might not get their first choice of nursery or childminder.
"I know it's not what parents want to hear but this Labour government is one of service.
"We will always be honest with the public."