There are "fundamental problems" with Ofsted inspections of nurseries and childminders, according to campaigners.
New figures show that two thirds of formal complaints made to the inspectorate in 2013/14 were filed by those working in early years education, the Pre-school Learning Alliance said.
The statistics, contained in Ofsted's latest annual report, show that of 1,809 activities complained about last year, 1,197 (66%) were related to "early childhood".
This is up from 48% the previous year, the Alliance said.
Alliance chief executive Neil Leitch said: "Early years inspections only account for around half of all Ofsted inspections, so the fact that 66% of formal complaints and 72% of internal review requests come from early years providers suggests that there is a fundamental problem with the early years inspection process.
"While we welcome the fact that Ofsted has started to engage with the sector on certain issues, such as the growing prevalence of complaint/concern-driven inspections, it's clear that there are still many questions to be answered over the quality, fairness and consistency of all early years inspections."
He added: "While Ofsted has now taken steps to address concerns over the quality of school and further education inspections by bringing them back in-house, this approach has yet to be extended to the early years sector.
"These figures should send a clear message to Ofsted that it must look to improve the quality of early years inspections as a priority. This is simply not possible under the contractual arrangements and so we continue to urge Ofsted to reconsider to its current stance on this point."
An Ofsted spokesman said: "Our early years inspectors all have a background in the sector and make judgments based on what they see and know about a nursery or other kind of early years setting. All inspectors work within a national framework which ensures consistent standards.
"If however an early years provider is unhappy about the judgment on the quality of the setting then they should raise the matter with us as soon as possible.
"We are working through wider changes in the early years sector. For example, we do not yet know the impact of childminder agencies. As a consequence, we do not think it is the right time for large contractual change."
Ofsted statistics published earlier this year showed that thousands of nurseries and childminders are still not giving youngsters a good standard of care and education,
The data revealed that as of the end of last October, more than a fifth of early years providers (21%) were rated as "satisfactory" and a further 2% were considered to be "inadequate".
It means that overall, around 15,300 nurseries and childminders were judged as less than "good" at their last inspection.
Two thirds (66%) were found to be "good" while 12% were "outstanding".
Early years inspection were revamped by Ofsted last November.
Under the shake-up, the old ''satisfactory'' rating was scrapped and replaced by ''requires improvement'', a change which has also been made to school inspections.
Announcing the changes last year, Ofsted chief inspector Sir Michael warned that inspectors will be tougher on poor nurseries and pre-schools, because ''no one thinks they should be allowed to languish in their inadequacy''.