The man heading the review of 14 to 19 learning in England says he does not believe ministers are looking to water down his proposals.
The next 10 years are expected to see big changes
A government source had suggested the need for change had "receded".
But Mike Tomlinson - former chief inspector of England's schools - said he detected no hint of backtracking.
His working party's plans for new diploma qualifications are due to be published in their final form next month.
The Guardian newspaper on Monday quoted an unnamed senior government source as saying: "There is a feeling that the need for change has receded. The exam season this year went very smoothly."
There was the "challenge" of balancing short-term change with longer-term reforms, and what would be "palatable" for schools and parents.
The source added: "I think it's fair to say there's a lot more evaluation to do."
John Dunford, general secretary of the Secondary Heads Association, said he would be very alarmed if this meant the reforms were to be diluted.
"I think it's very important to maintain the momentum for change," he told BBC News Online.
Mr Tomlinson had sought and successfully achieved a very broad consensus for change, he said.
"I think it's vital that all three political parties sign up for it so we don't have a row about it at the next election."
On Wednesday, Mr Tomlinson told BBC News Online that he expected the government to respond fully to his proposals "probably at the turn of the year".
He had received no indication from his discussions with ministers that their commitment to reform had lessened.
Indeed he had been at a Labour conference fringe meeting with the School Standards Minister, David Miliband.
"Far from backtracking there was solid support for the principles," he said.
As for the timing, he expected Mr Clarke to say there were some difficult matters to resolve that would require further work - but that was as it should be.
Unlike the rushed Curriculum 2000 reforms, it was important that such a major change should be piloted, he said.
"What we are not going to offer him is an oven-ready package which, with a click of his fingers, he could implement from day one," Mr Tomlinson said.
"So I am not worried."
Also at the Labour conference on Monday the Education Secretary, Charles Clarke, said: "There is a consensus for change but the issues are very difficult and problematic."
He acknowledged a desire to move quickly, but added: "It's an enormous agenda. I believe it's genuinely a 10-year agenda - these are very difficult issues."
He has set five key tests for the Tomlinson reforms.
They must stretch the most able students, provide high-quality vocational education and prepare all youngsters for work, reduce the burden of assessment and encourage more youngsters to "stay on" after the age of 16.
Mr Tomlinson declined to be drawn on the detail of his final report.