Speaking at the Association of County Councils conference in Leicester this morning, Sir John said unitary authorities appeared more efficient - in theory - but there was no hard evidence of this.
'I know of not one single solitary shred of evidence - from the academics, auditors or practitioners - to suggest that unitary authorities are in fact better than the existing two-tier structure at managing truancy, juvenile crime, care in the community, homelessness or care for the elderly.'
Sir John said the Association of District Councils' proposals on unitary authorities would have cost up to £400m in transition costs had they gone ahead.
However, where it saw fit, the commission had recommended unitaries for areas covering a total of over 2.7 million people, a combined staff of over 80,000 and gross revenue expenditure of up to £3bn.
New unitaries would eventually represent over seven million people in England.
But Sir John said British people were pragmatists and wholesale transfer of power to unitary authorities on the basis of theory alone was not practical.