Bold commitments to slash class sizes across Scotland were a familiar theme across the political spectrum in the run-up to last May's Scottish Parliament election.

With Scotland's largest teaching union, the Educational Institute of Scotland, funding an advertising campaign promoting smaller class sizes, at times it appeared politicians were falling over themselves to promise the most radical reductions.

Nearly a year on and the legacy of this bidding war is clear. The SNP - which emerged triumphant from the Holyrood elections partly because of its manifesto commitments to cut classes in P1-P3 to a maximum of 18 - now must deliver.

Under the terms of the concordat signed with local authorities, councils have been charged with "year on year progress" to meet targets "as quickly as possible".

However, documents released under Freedom of Information legislation to the Scottish Liberal Democrats have revealed the true scale of the task and raise question marks over whether annual progress is achievable.

Fifteen of the 32 local authorities have no strategy to implement the policy. Many who do are unclear how the target will be met.

The most vociferous opposition comes from Labour-led Glasgow City Council, where officials will not pursue the targets after costing them at £45m.

Gordon Matheson, executive member for education, said that rather than pursuing the Scottish Government's "flawed and totally unfunded class size reduction policy", Glasgow would be focusing on numeracy and literacy.

There is embarrassment for the SNP given that some local authorities yet to produce a class-size strategy are partly run by its own councillors.

Aberdeenshire Council, jointly run by LibDems and SNP, say: "With around 300 classes to reduce to a maximum of 18 pupils, we are not able to make this a priority. These costs would not only be in paying for the additional teaching staff, but it would also involve the cost of renovating or extending many of our schools."

East Renfrewshire, run by a Labour/SNP coalition, has not fully developed a strategy "pending notification of any possible additional funding".

Edinburgh, where there is a LibDem/SNP coalition, has no strategy, but intends to publish one. Highland, where independents and SNP share power, stated: "No formal strategy has been approved. It is unlikely that a report would be submitted to the elected members before November."

In Perth and Kinross, which has an SNP/LibDem coalition said: "Work is in progress to assess the implications."

In West Lothian, where power is shared between independent councillors and the SNP, officials said: "West Lothian Council has not yet documented a strategy."

Angus said it had not set a specific strategy as the reductions were dependent on factors "outwith the education department's control". "The supply of suitably-qualified teachers will have a major impact on the ability to meet this target," officials said.

In Dumfries and Galloway councillors have not yet considered the issue "specifically", while in Moray there are "no detailed plans post 2010" but the council aims to move to a maximum of 25 by 2009.

Borders said: "With rising rolls in the primary sector the council cannot make any solid plans." And South Lanarkshire's position is: "At the present time, no decision on the reduction of class sizes for P1 to P3 has been taken."

Dundee, East Dunbartonshire, Stirling and North Ayrshire are in discussions.