GCSE exams are to be replaced by a qualification known as the English Baccalaureate Certificate, Nick Clegg and Michael Gove have said.
Writing in the Evening Standard the education secretary and deputy prime minister said the "radical reforms" would require "careful preparation".
"We propose introducing new English, maths and science certificates in September 2015 with other subjects following.
The announcement came an hour before Michael Gove is due to make an official statement to the House of Commons regarding the new exam system.
The article, published on the Standard's site at 3.30pm, would have coincided with Gove's official statement to MPs but this was pushed back by an hour due to an urgent question tabled by Labour on Afghanistan.
Clegg and Gove said the new qualifications would be dubbed the EBacc - a name which currently exists as an umbrella term for a combination of core GCSE subjects.
The duo added: "They are the foundation on which further study, vocational learning or a satisfying apprenticeship can be built. Success in English, maths, science, a humanities subject and a language will comprise the full English Baccalaureate.
"In the battle to make our society more open, mobile and free it has been good to know that by working together we can overcome those forces that have held our children back — the entrenched establishment voices who have become the enemies of promise."
Many students, posting on TheStudentRoom forum, welcomed making GCSEs harder.
"I would make GCSEs a little bit more challenging so that it could bridge the gap between GCSEs and A-level study," on student wrote.
"I would change the current GCSE qualification, and in so doing, make it harder for people to just rote learn the syllabus and the mark schemes and get a good grade without actually understanding the subject."
Gove and Clegg added special provision would be made for students not sitting the mentioned exams and schools would be required to detail their achievement in each curriculum area to help them progress.
"These reforms are radical — so we will consult widely," they added. "Their introduction will require careful preparation. So we propose introducing new English, maths and science certificates in September 2015 with other subjects following."
Professor Robert Coe director of the centre for evaluation and monitoring at Durham University, said coursework is not the problem.
“Coursework and modular exams have been getting a bad name recently but there are good educational reasons for including both in assessments. The problems come when you combine them with a high-pressure accountability system that includes league tables, closing down schools that don’t meet ‘floor targets’, and the general perception that exam results measure educational quality. The truth is that no kind of assessment can really withstand this kind of pressure.
“It is not obvious how the new qualification will be different from GCSEs. Of course you can give it a new name and say it will be rigorous and be like the O-levels were, but what does this mean?
“People like the idea of the O-level exam because it represents an elite, high standard.
“There are certainly problems with the current GCSE, and it is right to make it more challenging for the highest attainers. Exam questions have relied too much on recall of facts, requiring regurgitation of formulaic and predictable responses rather than understanding or hard thinking. If the new exams better reward the kinds of learning we actually value then the change will be very welcome.”
Christine Blower, general secretary of the National Union of Teachers, called the proposals a "blatant two-tier system".
"The premise for the Government’s changes appears to be based on the rather spurious reason that too many pupils are succeeding.
“What is being proposed here is blatantly a two-tier system. Pupils who do not gain EBacc Certificates will receive a record of achievement which will most certainly be seen to be of far less worth by employers and colleges.
“Placing a cap on those who can gain top grades means that many students will miss out on the recognition and opportunities they deserve and harks back to a time when only a few were expected to go on to higher education.
"Setting up examination systems to ensure only a few succeed is counterproductive."