Schools Minister Lord Adonis says that by 2020 four fifths of England's teenagers should get five good GCSEs.
A generation ago it was a 20% system, Lord Adonis said
Last year the figure was about 60%, or 44% if English and maths were included.
Speaking at the Cass Business School in London, Lord Adonis said 80%, on even the tougher measure, was an "ambitious but realistic" goal.
But the Conservatives said the risk was that schools would push children even more into less academic subjects in trying to attain it.
Lord Adonis said: "Eighty per cent requires relentless improvement, but not at an unrealistic rate if our will is matched by concrete and credible policies."
He said it was likely to provoke accusations that exam standards would be "dumbed down".
But he said it was a "realistic and realisable" aim.
Shadow education secretary David Willetts said everyone wanted to see higher school standards.
"But the danger of Lord Adonis' target is that schools try to meet it by encouraging children to take less academic subjects.
"Already schools are pushing students into non-core subjects that aren't as valued by employers and universities.
"Such a target then becomes a cruel trick on a generation of students."
Lord Adonis also said state schools needed to develop the sort of "old boy networks" that characterised Oxbridge and the independent schools.
"Anyone who knows anything about England's private schools and the advantages they confer on their students, realises the importance of their external partnerships," he told the meeting.
"I mean not just their 'old boys networks' but the dense web of their links to the professions and to higher education, including the leading universities.
"As a lecturer at Oxford I was struck by how many fellow dons served on the governing bodies of leading private schools, and how networked these schools were to Oxford. And how rare it was for state schools to have similar connections.
"We need partnerships of this kind to extend to all state secondary schools."