The private sector will be granted a greater role in education despite increasing criticism from within the Labour party, the Prime Minister said in his first major education speech for six months.
Tony Blair appealed for more private-sector sponsors to invest in education and backed a further expansion of the academy programme, which allows businesses to set up and run schools.
Attracting private money into schools will help British education to keep pace with other countries, he said.
The speech, at the official opening of the Business Academy in Bexley, south-east London, sent a clear signal to backbenchers who hoped that Mr Blair's difficulties over Iraq and the Hutton inquiry might force him to compromise on public-service reform.
Mr Blair was adamant that he will not be deflected from reform by supporters of the comprehensive status quo. Failure to provide high-quality education is the "true betrayal" of children, he said.
"We need to hold our nerve and not succumb to the cynicism which says there is something deep-seated and cultural about poor public services in this country," he said.
Bexley is one of 12 city academies. Ministers have set a target of opening at least 50 in the next four years. Mr Blair said: "I think it's possible, if we really put our minds to it, to go even further than that. There is huge untapped potential out there."
Academies were part of a fundamental change planned for the secondary-school system which would tailor education to the needs of individuals, he said.
David Miliband, schools minister, said that the challenge for schools was to achieve both excellence and equity. He told an audience of supporters of the National Academy for Gifted and Talented Youth that while pupils in England do well compared to their peers abroad, there is still a long tail of underachievement.
"We are in the relegation zone when it comes to equity but near the top when it comes to quality," he said.