Parents who send their children to private schools should not get a subsidy from the state, says Schools Minister Jacqui Smith.
Private schools want a subsidy for fee-paying parents
There had been calls at a meeting of heads of independent schools for a voucher or tax rebate for parents who opted out of state education.
But Ms Smith rejected such calls, saying she would rather invest money in cutting primary class sizes.
"It comes down to decisions about political priorities," said Ms Smith.
The education minister had heard calls at the annual Headmasters' and Headmistresses' Conference that parents who were paying fees for private school should not also have to pay taxes towards state schools.
There had been an "assisted places" scheme, scrapped by Labour, in which government had subsidised independent school fees for some parents.
Ms Smith said that she wanted to work in "partnership" with the private sector - but gave no support to calls for financial subsidies for private school fees.
"Some of you have called for government support for more assisted places," she said.
"But I don't believe in a system where only a few are given the keys to a room at the top, or where equality means everyone gets just one chance to do well.
"Isn't the answer to ensure that excellence and challenge, wherever it comes from, is drafted into the state education system rather than to provide a few with an escape route out," said the minister.
Ms Smith's comments were criticised by the conference chairman, Priscilla Chadwick, who said they showed the "old ideologies ... are still there".
Jonathan Shephard, general secretary of the Independent Schools Council, also called for a greater role for the private sector - particularly using its expertise to improve standards in science.
He claimed that a failure of the state education sector to produce scientists and engineers meant Britain risked becoming a "Third World" country.
"Despite a number of improvements in state results, the decline in maths, sciences, engineering and modern languages is insupportable and has to be reversed," said Mr Shephard.
A Department for Education and Skills spokesperson dismissed his claims as "nonsense".