The Government's testing watchdog is at odds with a major exam board over moves to have hundreds of thousands of national curriculum test papers marked on a computer screen.
It vetoed plans by Edexcel, Britain's only major profit-making board, to have some of this year's key stage 2 and 3 tests, taken by 1.2 million pupils, emailed to examiners and marked on screen.
The move was revealed as Ken Boston, chief executive of the Qualifications and Curriculum Authority, voiced fears about whether the public is ready for the wholesale computerisation of Britain's exam system.
Researchers have also expressed concern about e-marking, saying examiners could lose concentration if they faced periods marking long scripts on a screen. Dr Boston supports computerised exams and scanning pupils' scripts for on-screen marking, which he believes has the potential to transform Britain's "cottage industry" marking system.
But in a speech in Australia, he admitted that the "man on the Clapham omnibus" was not yet ready to accept rapid advances. "Is England ready to have A-level Shakespeare marked in Toronto or Brisbane?" he asked.
This year, Edexcel marked four million GCSE and A-level and vocational papers on screen and the figure is due to rise next year.
Other exam boards take a different view from Edexcel over the growing pace of technological change. By 2008, all 14-year-olds will be able to take an on-screen ICT test. By 2010, the QCA wants pupils to be able to take some modules of most exams at the screen.
Other reforms include the chance for pupils to sit interactive computerised exams at a time of their choosing and the use of markers around the world to mark longer answers on screen.
The issue of on-screen marking of essays is particularly contentious.
Edexcel said it has no plans to trial the marking of long answers overseas.
However, its examiners have marked longer essays on screen in Britain.
Britain's largest board, AQA, which marked 750,000 GCSEs this year on screen, said longer essays would not be marked electronically unless it was confident that examiners could conduct a "proper evaluation" of work.
Cambridge Assessment, parent body of the OCR board, which is a rival of Edexcel, said more research was needed to check if examiners' on-screen judgements were accurate.
It found annotation was easier on paper than at the computer, and that examiners found it easier to get an overall sense of a text by reading it on paper. There was no evidence of marking disparities between the two methods.
Minutes of a QCA board meeting from May reveal that Pearson Education, the publishing company which owns Edexcel, sought compensation after its plans to have the 2005 tests marked on-screen were rejected.
An Edexcel spokeswoman said the company had conducted extensive trials of GCSE, A-level and vocational exams, which had been closely monitored by the QCA. The QCA said the technology of on-screen marking had been proved to be successful for these exams, but that more trials were needed before it was introduced for national curriculum tests.