Experts question push for greater participation when many centres not doing enough to help infants learn.
Education Minister Hekia Parata has not answered questions about whether she believes a report on learning for under-3s will affect a key Government target.
The Government is aiming to have 98 per cent participation in quality early childhood education by 2016 as part of the Better Public Services programme.
Last month it announced participation was at 96.1 per cent, and it was intensifying engagement with priority communities to reach the target.
However, experts say an Education Review Office study of 235 services released this week should have an effect on those figures.
The study found that while services were warm and nurturing, almost half of services were not doing enough to help babies and toddlers learn, with 30 per cent having "limited responsiveness" and 16 per cent deemed "not responsive".
Academics say the failure to uphold the curriculum sections that explicitly deal with extending children's development - communication and exploration - mean those services could not be called "quality".
Otago University emeritus professor Anne Smith, an expert in early childhood education, said there were two parts to "quality".
"There's physical things like group sizes and staff qualifications, and process quality, which is the responsiveness we're talking about: responding when children talk and communicating with them," Dr Smith said.
"We've been saying for a long time that it's all very well increasing quantity but if you don't increase quality as well it can be harmful, particularly for those in deprived circumstances."
The Herald asked Ms Parata twice yesterday if the report would affect the target, and asked for a definition of quality. There was no reply by deadline.
In response to other questions about the report, the minister said it showed ECE services were doing a great job caring for and nurturing children, but some needed support to lift the quality of curriculum delivery.
"The report shows us most services are doing a good job promoting positive learning outcomes for infants and toddlers," Ms Parata said. "But we know for a number of others there's more work to be done and that's what's ... being supported by the ministry and the sector."
The ministry would follow up on the report and help those who needed it with more professional development. A new joint initiative with the NZEI teachers' union and the ministry also had the potential to lift quality, she said, as well as other work.
The NZEI union and the Green Party criticised the Government for pushing participation when it knew there were quality issues.