Graham Donaldson, the architect of a major report on the future of teacher training, made the claim to Holyrood's education committee.
"In terms of what we call numeracy, as opposed to mathematics, the people who have actually attained quite highly in terms of mathematics skills, in terms of basic numeracy are not performing as well as they should be because that is not what has been reinforced and developed throughout their careers," he said.
However, Mr Donaldson, a former chief inspector of schools in Scotland and an honorary professor at Glasgow University, said the issue could be resolved with targeted lessons.
"There is no reason at all why anyone who has the qualifications to enter teacher training should not, by the time that they have completed, have the kind of literacy and numeracy skills that are required. I am very confident of that."
Kay Barnett, convener of the education committee of the Educational Institute of Scotland trade union, said: "It is about making sure there is support there."