the Scottish Government has been criticised for ignoring its manifesto pledges on smaller class sizes.

The attacks follows claims by Education Secretary Michael Russell that he was open to suggestions extra teachers were best targeted at the early years or at schools in deprived areas.

In 2007, when the SNP came to power, it promised to deliver classes of just 18 in the first three years of primary school.

But the only firm commitment that has been introduced is a maximum of 25 in P1, which has been enforced by legislation.

Larry Flanagan, general secretary of the Educational Institute of Scotland (EIS), said: "We believe the only way to ensure smaller class sizes is through statute, which would both set legal class size limits as well as halting any possible postcode lottery of class size levels.

"We welcome Mr Russell's acknowledgement of the case for reducing class sizes, especially its potential impact on reducing disadvantage.

"The Scottish Government, however, made clear manifesto commitments to reduce class sizes before it was elected and we are concerned the flexibility that has been offered to allow local authorities to determine their own priorities for class size reductions effectively renders that Government commitment meaningless."

Hugh Henry, education spokesman for Scottish Labour, said: "The SNP Government was told by its civil servants in 2007 that its promise could not be delivered.

"International evidence shows the quality of teaching, and the support and resources available to the teacher, are the most important things which drive up standards.

"Mike Russell is now trying to put a gloss on the reality that the SNP budget cuts are pushing up class sizes across Scotland."

Yesterday, Mr Russell said: "I am clear there is evidence that in the early years, particularly in areas of deprivation, smaller class sizes do make a difference.

"I am keen to explore the extent to which our policies on class sizes can play a role in delivering improved outcomes and closing the attainment gap."

He also announced a new scheme to twin secondaries that underperform in exams with successful schools in similar catchment areas in a bid to drive up standards.

Schools in deprived areas will be involved in the Scottish Government programme to break the link between poverty and underachievement. But secondaries in middle-class areas, seen as coasting, will also be targeted in the initiative.