In April Mr Richards accused Mr Woodhead of distorting inspection evidence in order to present a relentlessly negative picture of primary education. He has now turned his attention to the report on reading in three inner-London boroughs, published by OFSTED in May.
The report condemned the low levels of achievement found in 45 primary schools in Islington, Tower Hamlets and Southwark, attributing this to poor leadership on the part of heads, weak teaching, and "a commitment to methods and approaches to the teaching of reading that were self-evidently not working".
The fall-out from this report brought a promise from Gillian Shephard, the Education and Employment Secretary, to "recast" teacher training and to introduce a "national curriculum" for teachertraining courses.
Mr Richards resigned from OFSTED in March but was senior primary adviser while the reading survey was being carried out. On Sunday, he told a conference organised by the National Union of Teachers at Grantham that the inspectors could not possibly have come to these conclusions on the basis of the lessons observed.
In particular, he takes issue with the report's claim that the pupils were not making the progress they should. "It is invalid," he said, "to make any evaluation of progress based on the inspections methods used."
He says that inspectors visited the schools once, and heard children read once; they did not know the schools, and did not return. "It is a simple logical point - it's impossible to make judgments on progress if you only judge children at one point in time.
"It may well be true that the pupils were not making adequate progress, but the report should have restricted itself to what it could say. It reports as findings things it could not possibly know."
He went on to speculate on why this had happened: "Are the references to progress a matter of sloppy drafting, or someone's inability to appreciate what can and cannot be said on the basis of methods used, or a deliberate attempt to mislead?"
He also questioned the direct causal link made in the report between weak teaching and poor progress. "The report does not justify it. When you say that two things are happening, you have not necessarily proved that one causes the other. There are many other factors that can affect progress in reading, such as having English as a second language, parents' attitudes, children's background. . . weak teaching may well have contributed, but the report cannot assert it as fact."