The pace of change in England's schools must not be allowed to slow, Education Secretary Alan Johnson has said.
Mr Johnson will dismiss 'rubbish' talked about trust schools
In his first speech in the job, Mr Johnson argued Labour would "lose the argument and may well lose office" if it stops reforming.
The comments came after the Education Bill, which will bring in independent trust schools, got through the Commons on Wednesday thanks to Tory votes.
The Conservatives said Labour was "divided and paralysed".
Mr Johnson urged a "refreshed and revitalised radicalism" on his party's MPs, 69 of whom voted against the government.
'Must push ahead'
In his speech to the Fabian Society in London, he said: "England's schools are today in a better state than in recent memory.
"But our educational history has been one of continuous improvement and continuous reform.
"We must push ahead with a refreshed and revitalised radicalism in our schools policy.
"If we don't, we will lose the centre-left consensus that has joined our movement together for over 100 years.
"We'll lose the momentum, lose the argument and may well lose office."
Tony Blair's controversial education reforms cleared the Commons by 422 votes to 98 on Wednesday - a majority of 324.
The reforms, first outlined in a white paper last year, have provoked large-scale dissent on the Labour backbenches.
Opponents have said trust schools, given more say over budgets and admissions, will lead to more "back-door" selection of pupils.
But Mr Johnson said "more and more" head teachers are keen for their schools to adopt trust status.
He added that the reforms "offer an opportunity to improve performance, which is only difficult to contemplate if you believe the rubbish that has been talked about what a trust school means".
After the Commons vote, Labour MP John McDonnell - one of the backbenchers who voted against the government - said: "New Labour is in free-fall and the opposition is increasing, not declining."
Shadow education secretary David Willetts said: "This is the biggest rebellion Labour have had on the Third Reading of a Bill since they first came into office in 1924.
"Normally rebellions fizzle out by Third Reading, but even at this late stage Labour have lost their majority.
"It shows Labour are divided and paralysed. Conservatives are united and the only party that can deliver real reforms in our schools."
Liberal Democrat education spokeswoman Sarah Teather said: "All the elements of the bill that concern us remain - questions over fairness in admissions, accountability and regulation of trust schools.
"The reason this bill has provoked opposition within the prime minister's own party as well as amongst Liberal Democrats is because these measures are not what parents are asking for."
Outspoken Labour critics waiting for the draft legislation as it moves to the House of Lords include former leader Lord Kinnock and former education secretary Baroness Morris.