Jim Fletcher, education convener in East Renfrewshire, said all four-year-olds now have access to a nursery place and parents have shown a preference for council provision. As a result 250 extra places have been provided.

But Mr Fletcher warned: “Vouchers are not an efficient or clever way to increase nursery provision. The message from our experience is that all education authorities need to be able to run nursery education, and vouchers are just a sideshow.”

Val MacIver, education chairman in Highland, said voucher income covered the scheme’s running costs in her authority but stressed that this was “a very early estimate”. The council has raised the number of nursery classes from two to 11, providing 305 places instead of 80. Thirteen playgroups and one private centre offer 100 additional places.

Mrs MacIver said Highland had incurred costs of Pounds 80,000 for which it received no Scottish Office funding. While the administration of the vouchers was relatively simple, the administrative costs could be prohibitive for rural areas.

Argyll and Bute, where pilots are running in three mainland and three island areas, reported that some projects are on the margins of viability. Eleven new council units had created 210 places but there was only one voluntary group among 31 providers.

Despite their reservations, however, councils will join the Scottish Office’s voucher implementation advisory group. “If you ain’t in there, you ain’t going to influence anything,” Alec Thomson, education convener of the Convention of Scottish Local Authorities, said.

Meanwhile Helen Liddell, Labour’s education spokeswoman, told private nursery leaders that the party’s blueprint for under-fives education, published last week, envisaged 25 pilot “early excellence centres” throughout the UK. Two of these would be in Scotland, providing a model for combined nursery education and child care.