The union says it has been forced this week to submit its claim for a four-level career structure to the 32 local authorities individually because employers refuse to discuss it on a Scotland-wide basis.
Carol Ball, who chairs Unison's nursery nurse working party, said the Convention of Scottish Local Authorities had refused to enter national negotiations despite the fact that there are supposed to be national terms and conditions and despite the national framework for nursery nurses recently established by the Scottish Executive.
But Cosla accused Unison of "mischief-making". The authorities say nursery nurses are subject to a job evaluation exercise agreed three years ago for all local government staff. No decisions could be taken on a national grading scheme until that is complete, Frank Russell, Cosla's spokesperson on personnel matters, said.
Unison, which says it represents 90 per cent of Scotland's nursery nurses, insists a new structure allowing nursery nurses to move from basic grade to head of establishment is necessary to reflect increases in their duties since 1988.
This will involve substantial pay hikes for staff whose annual earnings average around pound;12,000.