There could be as many as 30 primary one pupils to a class in Edinburgh next year, despite SNP pledges to reduce numbers.

The City Council has confirmed it may be forced to increase its P1 class size limit to 30, despite the Nationalists manifesto promise to cap it at 18.

The Scottish Government announced plans to introduce legislation to limit primary one sizes to 25 this year, ahead of further reductions in future, and Edinburgh City Council had been working to that limit in recent months.

However, with the school placement process already well under way, no legislative action has been taken and council chiefs fear they will be left open to legal actions from parents if they do not return to the current legal limit of 30 children per class.

Council education leader Marilyne MacLaren said: "We are committed to reducing class sizes and we have taken big steps towards making this happen across the city."

"However, the reality is that if we don't have a 'back-stop' to cap classes at a maximum of 25, it is highly likely that 50 other schools will see numbers go beyond 25. 

"If we aren't going to see new regulations then we will have no option but to increase the limit to 30 in line with current legislation. This at least should keep class sizes more manageable for teachers. This is disappointing but without legal protection from the Government we don't have any other option."

Councillor MacLaren added that she "fully expects" the authority to meet the Government's target of 18 or fewer pupils in 20% of primary one to three classes by August.

A Scottish Government spokesman said: "While it is not possible to now legislate to meet the deadline for placing requests made before March 15, we still intend to consult on regulations and have them in place by the autumn.

"It is unlikely that placing requests will impact upon local authorities achieving 20% of P1-P3 pupils in classes of 18 or fewer, as councils will be targeting schools in areas of deprivation where placing requests are less common and class-size reduction is likely to have the greatest impact."

Legal challenges have shown that schools should expect to face placement requests from parents outside their catchment areas.

South Lanarkshire Council has lost 19 legal challenges in the past year from parents, meaning authorities could be left with no choice but to accept children up to the legal limit of 30 pupils.