This policy pledge covers just half the 1993 recommendation by Sir Claus Moser's National Commission on Education, which urged nursery education for all aged three and four.
Debate is raging between the right and left wings of the Cabinet on how to fund this big expansion of state provision.
The right is said to favour a voucher system, a preference which appears to be prevailing at the moment.
The latest suggestion is for a voucher worth pounds 1,000 per child, which parents could spend at any local authority or approved private nursery. Some playgroups may also qualify. It is unclear whether this would be means-tested, or a universal benefit.
It is clear, however, that in a high proportion of institutions, in both the private and public sector, pounds 1,000 will not pay in full for quality nursery education.
The shortfall would either mean parents having to top up the money from the state in order to purchase the desired level of education; alternatively, access would be limited, in terms of the hours purchased, or the quality of services.
Current pre-school provision for under-fives is a patchwork, consisting of full- and part-time, state and private, educationally focused or day- care institutions.
Some are regulated by the Department of Health - these include often full-time private and local authority day nurseries, playgroups, and registered childminders. Infant school reception classes and, usually, part-time nursery education come under the Department of Education.
It is not yet known if all of these would qualify for vouchers - child- minders and some playgroups would probably be forced to raise their standards.
Vicky Hurst, vice-president of the National Campaign for Nursery Education, and lecturer in early childhood education at London's Goldsmiths' College, says state nursery provision costs pounds 3,000 per annum, for a 9.30am to 3.30pm school day (although the more standard half-day costs half the sum.)
Ms Hurst says average full-day private sector nursery fees amount to pounds 5,000 or more. These range from pounds 70 or pounds 80 per week outside London and the Southeast, to as much as pounds 160 or pounds 200 in central London.
Sending a child to a childminder can be a cheaper solution, at pounds 60-75 for a 40-hour week. Here, however, workers do not possess the same level of educational training as state nurseries (and some of the private ones). Their facilities are sometimes lower-grade than those of nurseries - for instance, there may not be a suitable outdoor play area.
Morning or afternoon-only sessions are proportionately cheaper for nurseries and child-minders.
The lowest-cost service is supplied by playgroups, where a session can cost as little as pounds 2 or as much as pounds 6. The staff are low-paid, sometimes voluntary.
Some four-year-olds are admitted a term or two early to infant school reception class. This costs around pounds 2,000 a year. But the National Campaign for Nursery Education considers reception class an inappropriate and inhospitable place to send a child as young as four years old.
David Whitbread, undersecretary for education at the Association of County Councils, believes further problems would arise with a voucher system. "National provision for four- year-olds won't be feasible unless extra capital sums are available for country and newer housing areas, where no services presently exist. Vouchers just won't be enough to cover the start-up costs,'' he said.
In these areas, where there could be fewer children of any particular age, establishments may not get sufficient numbers to be able to run without some sort of additional help.
Mr Whitbread feels the administration of any voucher system will be fraught with difficulties.
For example, how do you account for a half-year's education should the parents decide to move to another area and wish to resume the child's education there, halfway through the voucher year?
Maintaining the pupil-to- teacher ratio will be another problem. Within the state nursery sector, two professionally trained adults are required by law for every 26 children, or one for every 13.
If the class reaches 26, it will be running at capacity, and the cost per staff member will be low. This will shoot up, however, if a single new toddler joins the class, and an extra teacher or nursery nurse has to be taken on. Voucher money will not increase sufficiently to cover the additional expense.Reuse content