Colin Richards, professor of education at St Martin's College in Cumbria, wants inspectors to be given advice on writing about language development in young children without giving offence.
In letters to Mike Tomlinson, appointed acting chief inspector of schools, he cites the report of a school where 66 per cent of children did not speak English as their first language.
Comments about under-fives in the school included: "At the time they enter key stage 1, pupils' speaking skills are underdeveloped. The number of words they have available is limited, and many of them can only put them together in a basic way."
Another report in a similar school said: "Many pupils enter schools with very poor skills in areas of language and literacy."
Professor Richards, former chief primary HMI, said eight or nine of the 40 inspection reports he has looked at in detail this year contain quetionable comments which could give offence.
"When inspectors talk about language development, they need to make clear they are talking about the development of English," he said.
Other reports make comments about social and emotional development which are not appropriate for such young children, he added.
"It is not clear to me how far the Office for Standards in Education takes account of ethnic background when judgments are made about standards."
Private correspondence from Mr Tomlinson says OFSTED is preparing a training package for inspectors that will cover such issues. Changes are also being made to the manual followed by inspectors.
The Commons select committee last week criticised Chris Woodhead for failing to meet researchers from the Commission for Racial Equality.
Its chairman, Gurbux Singh, described correspondence over the matters as "offensive".
An OFSTED spokesman said: "The areas of concern covered by Professor Richards will be covered by the new training given to all inspectors."