The Conservatives say they will introduce tests for 14-year-olds in all compulsory national curriculum subjects if returned to power.
Pupils would sit nationally-set tests in an additional seven subjects, with the results presented in a certificate of education at the end of year nine. The certificate would also form part of each child's national record of achievement.
The pledge is intended to put further "clear blue water" between Labour and the Conservatives, and will be featured in the Tories' election manifesto launched next week.
But a press statement was released this week amid some confusion, with both teachers' leaders and Opposition politicians accusing ministers of muddle and lacking a coherent approach to policies.
In her statement, Education and Employment Gillian Shephard said the results of the tests would help pupils choose their GCSE subjects, part one GNVQs or other vocational courses being piloted in key stage four.
They would also help schools and teachers identify their own strengths and weaknesses. The results would in time be published.
Extra subjects to be tested include: technology (including design and technology and IT), history, geography, art, music, PE and a modern foreign language.
"It will reinforce the importance of all subjects in the curriculum and the need for them to be well-taught and well-learned," Mrs Shephard said.
If the Tories are returned, the tests would be unlikely to be introduced before 1999.
A source close to Mrs Shephard said: "It is clear blue water and I suppose it will put Labour local education authorities in even further disarray." She admitted the tests would mean extra work for teachers but said full consultations and pilot schemes would be carried out. Like other national assessment tests, which were introduced in the face of great opposition from teachers, the papers would be externally set and marked.
The announcement was strongly opposed by Peter Smith, general secretary of the Association of Teachers and Lecturers, who said the tests would be likely to demotivate far more children than they would spur on. "Ironically it could actually worsen truancy figures and exclusion rates rather than improve them. Children could be leaving school effectively two years early because they have this badge of failure."
David Blunkett, Labour's education spokesman, said: "It conveys the message that it's just as worthy to achieve a high mark in music or PE as it is in maths. It increases opportunities for all children. If this is the best the Tories can do after 18 years, it is pretty small beer."