A curriculum for Excellence will fail if schools and teachers are left to "deliver it on the cheap", according to one of its biggest supporters.
Ronnie Smith, general secretary of the Educational Institute of Scotland, claims that teachers are being asked to make radical changes despite "an acute absence of support, resources and development time".
He welcomed the recent decision to delay implementation until 2010, but warned that even that would not allow enough time at the current rate of progress.
"Some councils have been lauding themselves for leading the way in the development of Curriculum for Excellence," he said. "However, the message from teachers is that this alleged progress is often not apparent at school level.
"Most teachers do not believe they have been engaged with fully on this, the most significant change to teaching for a generation."
The most important resource, he said, was time for teachers to work on development of the new curriculum. He also called for a "properly funded and adequately resourced" programme of professional development.
But he said teachers believed money which would have gone towards A Curriculum for Excellence was now being spent elsewhere, following budget cuts resulting from the concordat between the Scottish Government and local authorities.
"As is so often the case, in-service training is the first casualty of budget cuts," he said.
Mr Smith queried whether teachers were being asked to "create something out of nothing", which was "no basis for the transformational change" expected.
"The message from teachers in schools, right across the country, is that they support the ethos of the Curriculum for Excellence but that they cannot deliver it on the cheap," he said.
Despite his concerns, Mr Smith praised Education Secretary Fiona Hyslop for her "commitment and leadership" in pushing ahead with the new curriculum, and also for reacting quickly to concerns and delaying implementation for a year.
"I think the level of engagement with stakeholders is very good," he said. "I think she's shown herself to be quite sensitive to some of the messages coming through."
He warned, however, that the new curriculum must not get "blown off course by distractions", such as the proposed languages and science baccalaureates.
The idea might be a "sexy" one, but some schools were going to struggle to offer any Advanced Highers, let alone the several required for the new qualifications.
Another potential distraction was the recent Trends in Mathematics and Science Study (Timss) findings, which showed that Scotland was in the company of Third World countries in terms of 10- and 14-year-olds' performance in maths and science.
"Schools should hold their nerve and go forward, rather than make knee- jerk reactions to extraordinary events," he said. "The Scottish Government has got to find a way to make sure that the 32 local authorities keep their eye on the ball."
A Government spokeswoman said membership of the Curriculum for Excellence management board had been widened to include representation from teachers' associations and unions, including the EIS. The Government had paid "close attention" to their views, and the year's delay to implementation of A Curriculum for Excellence resulted from a recommendation made by the board.
"The overall programme encompasses consideration of implementation requirements including professional development," she added.