Government may have to introduce new legislation to inspect private nurseries if high educational standards are a prerequisite for vouchers.
The Office for Standards in Education is only allowed to inspect state nurseries, and the voucher scheme could herald an extension of its powers, said an OFSTED spokeswoman this week.
The Department for Education and Employment has made it clear that parents can only use vouchers at nurseries or playgroups which deliver education.
And although an increasing number of playgroups are being accredited by the independent Preschool Learning Alliance, the quality of the playgroup movement has been criticised by early years experts.
Education and Employment Secretary Gillian Shephard has said standards at under-fives establishments will be monitored through a "light touch inspection scheme".
The School Curriculum and Assessment Authority is to consult key early years' groups about the shape of a national nursery curriculum in the autumn so it can advise ministers by November.
The consultation will build on contacts SCAA made with the early years lobby last year, but which did not lead to any published report.
The DFEE wants a list of "desirable achievements" for children's learning by the time they begin compulsory schooling, and "possibly also guidance to providers on educational activities".
It will also require playgroups and nurseries to publish details of the number of staff and their qualifications, activities, premises and equipment.
Some early years experts question how OFSTED can inspect nurseries when it is already having difficulty meeting its targets for inspecting the nation's primary schools.
But Mrs Shephard said that Chris Woodhead, the chief inspector of schools, had assured her there would be no problem.