The Educational Institute of Scotland (EIS) call comes after the union lost a legal battle with Glasgow City Council to protect qualified staff.
It last night held a rally in Glasgow to protest over classroom workload and took action after Glasgow decided to appoint non-teachers as heads of its nursery schools.
After losing an appeal at the Court of Session in Edinburgh, the EIS said the ruling "seriously undermined" the Scottish Government's policy commitment to ensure "access" to a teacher for all nursery-aged children.
Figures published in December showed that more than a quarter of pupils in Scottish nurseries have no input from qualified teachers.
Larry Flanagan, EIS general secretary, said: "We believe qualified nursery teachers are an essential part of quality education provision in nursery schools, as indeed does the Scottish Government.
"The EIS launched this appeal with the aim of ensuring that all nursery-aged children could have meaningful access to a teacher in their school environment.
"Sadly, this ruling today will place teacher involvement in the education of young children in nurseries under very serious threat."
Eileen Prior, executive director of the Scottish Parent Teacher Council, said the organisation backed the principle that pre-school children should have meaningful access to a teacher.
"How this is achieved is likely to vary, but we know parents appreciate the perspective of a professional teacher," she said.
A council spokesman said: "We welcome this sensible decision which will allow us to be able to respond more flexibly to the changing needs of families for early years education and childcare."
A Scottish Government spokesman said: "We appreciate the important role played by teachers as part of the wider team in early years settings and the positive impact they make.
"That's why we are investing £460,000 over this financial year and the next to support additional postgraduate places for primary teachers wishing to specialise in early years."
In recent years, local authorities have replaced teachers with lower-paid child development officers - previously called nursery nurses - partly on cost grounds, but also because they work longer hours.
Councils argue that child development officers are better qualified than ever before, following the introduction of new qualifications up to degree level, and their use allows them to open nurseries for longer in order to meet the demands of working parents.
However, research has repeatedly underlined the importance of teachers to the quality of nursery education.