Children from disadvantaged backgrounds could suffer if Britain's exams system were computerised, Charles Clarke warned this week.
The Education Secretary told a London "e-assessment" conference that there was a danger of those without access to computers at home suffering.
He said: "The concern, that some people have that youngsters who do not have extensive access to computers could be disadvantaged, is one that has to be addressed up-front from the outset."
This warning was one of four potential problems which he spelled out at a time when the campaign for computerised testing is gaining momentum.
Dr Ken Boston, Qualifications and Curriculum Authority chief executive, told the conference that students should be given the choice of taking GCSE and A-level exams in most subjects on-screen within five years.
Laying out a demanding timetable for awarding bodies, he said they should be able to handle submissions of "electronic portfolios" of students' work in at least two subjects.
He said that by 2008 computerised GCSEs could be offered to students in some subjects "on demand".
Martin Ripley, head of new projects at the QCA, floated the idea of using virtual reality and computer game technology. Earlier this month, Dr Boston speculated that in future the public might take computerised exams in the pub.
Mr Clarke said e-testing could expand the types of assessment on offer to schools and be as rigorous as traditional exams. But he warned that the public would have to be convinced that the new types of tests would not be dumbed down.
He added that the system would need to be secure, so that it would be impossible for candidates to get someone else to sit the tests for them.
And assessments would need to be tailored to each national curriculum subject.
"On demand" GCSEs could bring fundamental change, Dr Boston conceded. Exam boards would have to prepare a bank of tests which could be allocated to students at any time. Mr Clarke has asked the QCA to produce a blueprint for e-assessment covering the next five years.