Nursery inspection reports are criticised as "poor quality" in a scathing report published this week by the House of Commons select committee on education.
The report, which was leaked to two national newspapers last week, is also highly critical of state primary schools "crowding out" private and voluntary nurseries in the race to cash in on the Government's nursery voucher scheme.
The select committee is worried about children who have just turned four being taught in reception classes; the Government targets for five-year-olds; the closure of playgroups and the threat to the education of three-year-olds; the lack of parental choice; the dearth of funding for training under-fives workers; and the "additional burden" the scheme places on staff time and energy.
The 83-page report concludes: "Overall, evidence from phase one (of the nursery voucher scheme) remains inconclusive on the likelihood of the scheme significantly expanding provision for four-year-olds in phase two."
The document, which was drawn up by seven Conservative MPs, five Labour MPs and one Liberal Democrat MP, is bound to embarrass the Government in the pre-election period.
Only three weeks ago, schools minister Robin Squire said: "Nursery vouchers work. The pilot areas have proved this. The prophets of doom who greeted this reform - as with so many others - have been proved wrong."
The committee criticises the "poor quality writing" of the reports by registered nursery inspectors. It says: "We recommend that the Office for Standards in Education continues to monitor, with great care, the standard of reports produced given the importance of the inspection system in informing parents about the calibre of settings and in raising standards of provision.
The committee has reservations about the organisation of the nursery inspections, and says "careful attention" should be paid to "the suitability and relevant expertise of inspectors". It also questions the value for money in inspections where only one or two four-year-olds attend a nursery or playgroup.
Early-years experts who have long criticised the practice of primary schools admitting younger and younger four-year-olds will also be cheered to read the committee's recommendation on reception classes.
"We recommend that the Department for Education and Employment examine ways in which the quality of education for young four-year-olds in reception classes could be improved," says the report.
"This could be brought about by a change in the staffing of primary school reception classes, for example by the employment of more trained nursery teachers and nursery nurses, or alternatively by making in-service training compulsory where the initial training of existing staff was not in the early years."
The committee also recommends that the DFEE should re-examine the decision to end the separate Government funding for in-service training of nursery teachers - another issue that has caused concern to the nursery lobby.
On the accusation that primary schools are "crowding out" other nursery providers, the report says: "If, during phase two of the scheme, more and more parents place their children in reception classes at the age of four - for whatever reason - there will in effect be a lowering of the age at which formal schooling starts, by a term or more.
"While in some cases this additional educational provision may be beneficial to the child, especially where the school has taken steps to ensure staffing and facilities are better suited to very young children, it is not clear from the evidence we received that this very significant step is being taken purely for educational reasons."