And pupils could face tick-box multiple-choice questions for the first time as part of the exam. They are likely to be able to re-take the tests as many times as they choose.
Yesterday the Government announced a new secondary curriculum allowing schools to devote more time to teaching English and maths to underperforming pupils. It said it would put a "relentless focus" on the basics of these subjects for struggling pupils.
The GCSE changes, which are about to be tried out in hundreds of schools in preparation for a launch in 2010, would represent the most radical alterations to the exam since the early 1990s. Ministers are taking seriously employers' complaints about teenagers leaving school lacking in literacy. No pupil will be able to gain a C or better in English, maths or ICT GCSE without passing functional skills tests. Such skills could also make up half of the maths and ICT exams.
Bethan Marshall, senior lecturer in English education at King's College, London, said: "If you make 50 per cent of the GCSE about doing the basics, you are dumbing down. The subject is about so much more than being able to communicate accurately. And if you're still doing basic skills at GCSE level, Heaven help you. It's pretty boring."
Ian McNeilly, spokesman for the National Association for the Teaching of English, said the move signalled primary literacy-hour-style lessons in key stage 4.
Draft outlines of the functional skills tests for English, maths and ICT have been published by the Qualifications and Curriculum Authority.
In English, pupils will be tested on how use a range of sentence structures, to punctuate accurately and use grammar correctly, to make verbal presentations and to detect bias when reading.
The Edexcel board, which has suggested the 50 per cent figure, also gives a sample question. Pupils are asked to answer which word is spelt wrong in the following sentence: "Be careful, the kettel is hot."
The AQA board has written to its pilot schools proposing that English GCSE is changed into a course of five modules, three of which would cover functional skills, including a multiple-choice reading test.
Functional skills tests in maths will see pupils being asked to convert imperial and metric measurements, work with fractions and use statistics. ICT tests will cover using the internet and formatting text.
The functional skills changes are still provisional; the QCA will announce firm proposals next year.
A spokesman for the authority said: "We recognise there are specific issues with regard to English. We will be working closely with the English, maths and ICT communities before any final proposals are put forward."
Curriculum review, page 4
Ed Balls, page 27