Peter Peacock made his remarks as the latest official figures were published showing that six out of 10 children who leave council care have no qualifications and are not in education, employment or training (the so-called NEET group).
Mr Peacock said this "second-class status" represented "a terrible indictment", and is demanding answers on how local authorities are spending the pound;10 million they were given last year to improve the attainment of looked-after children.
"Put simply, looked-after children are condemned to a life of difficulty because of failing services."
Mr Peacock said pointedly that councils had a legal duty to act as the parents of Scotland's estimated 11,400 looked-after children. "I will be monitoring very closely the actions they are taking to ensure we secure a better deal for these young people."
The Convention of Scottish Local Authorities reacted angrily to Mr Peacock's statement. Eric Jackson, its spokesperson on social work and health, said he was "disappointed". The Executive had to share the blame: setting targets and then expecting councils to deliver was not the way to solve the problem.
Pat Watters, Cosla's president, said "the real problem in this whole area has been a distinct lack of funding by central government for children's services generally. Scottish local government on the whole spends to a higher level on children's services than the Government's indicative figure."
The 60 per cent of 16-17s who left care last session with no qualifications compared with fewer than 10 per cent for the age group as a whole and the similar proportion in the NEET group compares with 14 per cent of all 16-19 year olds.
There was a wide variation in performance around the country. All 10 care leavers in the Borders had at least an Access award or Standard grade 5 or 6, compared with only 19 per cent of the 45 leavers in East Ayrshire.
The national average for those leaving care with a Standard grade 5 or 6 in English and maths was 26 per cent, but this ranged from 83 per cent in Orkney (five care leavers) to 7 per cent from East Ayrshire's 45.
Mr Jackson said the Executive had to take into account the fact that such children "have the decks stacked against them from an early age and throughout life, which makes prising the education door open, entering employment or training extremely difficult".