The qualifications regulator has rejected exam boards' claims that ministers are risking the success of the new 14-19 diplomas by introducing them too quickly.
Kathleen Tattersall, chair of Ofqual, published her first annual chief regulator's report yesterday, recommending new national qualifications should not be introduced without being "piloted in full" even if it meant a longer lead-in time.
But she told The TES it would be "foolish" to apply the stipulation - which follows grading problems over a new science GCSE - to diplomas retrospectively.
"I have been concerned that changes have been introduced too hurriedly without guarantees that the modifications to assessment models can be delivered reliably and will benefit learners across the ability range," Ms Tattersall writes in her report.
Her comments are about qualifications generally but echo exam boards' concerns about diplomas. Last month, Simon Lebus, chief executive of Cambridge Assessment, told the Commons schools committee that their introduction was "over hurried", "shaky" and added to an already "high risk". He also described ministers' aim of diplomas becoming the "qualification of choice" by 2013 as a fantasy.
All the major exam boards have urged government "in the strongest terms" to delay the 2011 introduction of the nine final phase academic diplomas. But ministers have agreed to postpone the advanced level science diploma only for a year.
Jerry Jarvis, managing director of Edexcel, told the MPs: "Money is being put on the diploma, so it has to work. But we just feel that it is too fast."
Ms Tattersall accepted the diplomas had not met the piloting framework proposed in her report. But they were being introduced in a "very phased", "measured and slow" way, she said. There would be an opportunity to review any case for delay after pupils had completed the first full-length diplomas in 2010.
Her report says Ofqual is having to address a "conundrum" between introducing modular GCSEs and A-levels that provide pupils with immediate feedback and ensuring that standards are in line with previous years.
It also notes a disconnection between 19th century-style pen-and-paper exams and young people for whom technology is second nature. Less than 50 of about 400 GCSEs and A-levels used "e-assessment".
Ms Tattersall said there would come a time when: "It is not natural for young people to sit down with a pen in their hand and write because they will be using laptops and PCs to do their work in school."
But that might not be for a few years because there were risks in changing the system too quickly. Good examiners who were not keen on technology might be lost, and it was important not to distort what was being taught by introducing multiple-choice questions that might not examine in enough depth.
Ms Tattersall refused to give her opinion on whether government observers should attend Ofqual meetings, a practice that Ken Boston, the former chief executive of the Qualifications and Curriculum Authority, believes will undermine the regulator's authority.