Secret documents, disclosed under the Freedom of Information Act last month, reveal how ill-prepared pilot schools were for teaching the foundation phase.
The papers show first drafts of the new play-led curriculum for three to seven-year-olds had to be completely re-written because they were so poor.
Teachers in pilot primary schools were then left to invent their own curriculum as contracted writers went back to the drawing board.
The full extent of early setbacks detailed in the documents include lack of interest in writing the curriculum, confusion over its content and poor quality of first drafts.
In one of the released papers, an official notes the first drafts "did not even come close to what was required or expected".
In another, teachers are praised for handling the curriculum crisis by coming up with imaginative ways of teaching the new syllabus.
Opposition parties demanded an urgent statement from education and lifelong learning minister Jane Davidson after the documents were made public last month. But this week she assured members that early teething problems surrounding the curriculum had been addressed.
She also revealed early findings of a draft evaluation into the first pilot year. In it, academics found that children taught by qualified teachers, rather than those in groups with higher adult-to-pupil ratios, had done best. But they also said many schools did not have suitable outdoor venues for teaching the new syllabus.
Opposition Assembly members are also concerned over the sheer volume of teachers needed. In her report to the Assembly's education committee this week, Ms Davidson estimated 1,800 new teaching staff are required. She said officials were currently working with local authorities to draw up a detailed workforce plan based on needs for the foundation phase.
The minister also said a huge training programme was crucial to the scheme's success, including training for key stage 2 teachers.
She said schools would be made "fit for purpose" for the foundation phase, and that moves had already been made to secure more adequate outdoor areas.
Janet Ryder, Plaid Cymru's shadow opposition spokesperson, said:
"If the report is saying that the foundation phase is better taught by qualified teachers, and not teaching assistants, then we will be struggling."
But Rhys Williams, communications, campaigns and political officer for the National Union of Teachers Cymru, said: "Wales presently has too many primary teachers - colleges should adapt their courses according to needs for the new foundation phase."
Pilots in 41 schools across Wales were up and running in September 2004.
However, full guidance material for all areas of learning was not in place until the beginning of this term. The national roll-out of the new learning programme has also been delayed by two years, and the foundation phase will not now be fully in force until 2010.
An extra pound;7.5 million funding for the foundation phase has been secured until the end of the pilot scheme in 2008. Slowing down the pace of roll-out means more schools - especially in deprived areas - will join the pilot programme.
Ms Davidson has also promised a greater synergy with the Flying Start programme, a scheme targeting toddlers aged 0-3, because of the delay.