The statistical discrepancies were revealed when the alliance compared quarterly figures released last year with Ofsted's report published in March, for inspections from 1 September 2012 to 31 October 2013.
The analysis shows that data on 425 full early years inspections is missing from the quarterly statistics covering early years inspection outcomes from April to June 2013, published last September.
Once these 'missing' inspections were added to the quarterly statistics, 9 per cent of providers were graded inadequate during this period, rather than the 7 per cent as stated in the quarterly figures. Moreover, in the previous quarter only 26 reports were missing.
Chief executive Neil Leitch said, 'Serious concerns are being raised about the entire early years inspection infrastructure: the fairness and consistency of inspections, the lack of transparency of the quality assurance process, growing delays in the publication of inspection reports, and now the comprehensiveness of official Ofsted data. These are concerns that Ofsted must address.'
An Ofsted spokesperson said, 'They are not comparing like with like. The provisional statistics published in September 2013 were about early years inspections that took place from April to June 2013 and used data as available at the end of July.
'That means that any Ofsted inspection that took place within those three months but did not yet have a published report was not included in our analysis.'
- Read Neil Leitch's comment