AS-levels could be scrapped under major reforms which are set to see re-sits cut and modules axed.
The move, outlined in proposals published by Ofqual today, would mean a return to traditional two-year A-levels, with exams at the end of the course.
Ofqual said that the proposal, one of three suggestions for the future of AS-levels, has been put forward amid concerns from some quarters that the qualification has resulted in students focusing on exams at the expense of other interests like sport and drama.
Under the current system, students sit AS-levels, which are qualifications in their own right, after one year of study, and can then decide whether to go on and study the second year to gain a full A-level.
Chief regulator Glenys Stacey insisted that Ofqual is "neutral" on the future of AS-levels.
Today's proposals also contain plans to limit re-sits so that a student can only re-take a paper once.
Research has shown that students "do not always treat exams seriously if they know they have the opportunity to re-sit," Ofqual said.
And the current modular system, in which AS and A-levels are split into two modules each, is also set to be axed.
Ofqual is proposing that in future, A-levels are no longer divided in this way as it makes it difficult for students to make connections between topics.
As expected, the exams regulator is also proposing that the January exam session should be scrapped, so that students can only take papers during the summer.
Ofqual's proposals for the future of A-levels in England, Wales and Northern Ireland are contained in a document published for consultation today.
Ms Stacey said: "A qualification as important as the A-level needs to be kept under regular review to make sure that it continues to meet the needs of its users.
"Our research shows where users think that A-levels could be improved.
"The consultation also takes into account the Government's wish that higher education becomes more involved in A-level development."
She added: "We know that people have different views on whether AS-levels should continue. We are neutral on this issue, and the consultation outlines a range of options on which we would welcome feedback."
Ofqual's document outlines three options for the future of AS-levels.
The first is to scrap AS-levels and return to a two-year A-level system with exams at the end.
The second is to make the AS-level a standalone one-year qualification with results that do not contribute to the A-level.
And the third is to keep the current system, but make the proposed cuts to re-sits and January exams.
There are different views about whether the current AS and A-level system should be kept, Ofqual said.
"We know that some stakeholders from higher education and teaching do support the AS qualification being kept," the document says.
"They believe that it increases the breadth of the curriculum, supports transition from study at Key Stage 4 and keeps open the further study options for students.
"We also know that some stakeholders from these same groups do not support the AS qualification being kept.
"They believe that the AS qualification has a negative impact on teaching time, limits synoptic learning and results in students focusing on examinations at the expense of the pursuit of wider interests such as sport, drama and volunteering."
The document also questions whether A-levels should be graded in a different way in the future.
At the moment, the exams are graded from A*-E.
"It may also be appropriate for new A-levels to be identified by a different grading system to prevent a two-tier system during the period of reform," it says.
There have been suggestions from some quarters that students could be given a mark alongside their grade to help universities differentiate between candidates.
Last month Ofqual said GCSE results could face a major overhaul, resulting in a cut in the number of grades available.
In its corporate plan, the exams regulator indicated that it was time to look at whether GCSE grades should still range from A*-G.
Today's document also sets out plans to give universities more control over A-levels.
It says that in future exam boards will have to show that for each A-level qualification it has the support of at least 20 UK universities, including 12 which are respected in the field or considered to be leading research institutions.
The new A-levels are all expected to be in place by 2018.
Ahead of today's document, the Russell Group, which represents a group of top universities including Oxford and Cambridge, said a move to cut A-level re-sits would be a "step in the right direction".
But it also indicated that an attempt to scrap AS-levels completely could be a step too far, as the qualifications are useful to universities.
Dr Wendy Piatt, director-general of the Russell Group, said: "While A-levels are broadly fit for purpose, we do have several concerns. With the current modular system, students too often quickly forget the 'bite-sized chunks' of knowledge they have learnt.
"This makes it harder for them to have an overall grasp of that subject, to synthesise information and to become independent learners. This consultation's proposals on ending the modular system and January exams are welcome.
"The proposed reduction in the number of re-sits that students are allowed to do would be a step in the right direction.
"We think it's fair that people are given a second chance if they have good reasons for under-performing in an exam, but more recently students have been allowed to do re-sits too frequently.
"Our universities are concerned that many of the students who don't get the grades first or second time around don't go on to do as well in their chosen degree course.
"AS-levels are useful to universities - as indicators of post-GCSE progress - and to students seeking to develop a broader range of knowledge."
A spokeswoman for Pearson, which runs the Edexcel exam board, said: "Qualifications and assessments need to motivate and reward deep learning that endures for all pupils.
"It is right that the review will address the design and the way A-level exams are delivered in practice by reconsidering modular assessment and re-sits and promoting synoptic assessment.
"We believe that the increasing tendency towards shorter and more numerous examinations has, for some subjects, led to too much focus on testing over learning. We do, however, see a continued case for the AS-level, as it offers pupils the chance to study a broader range for longer, and supports the university selection process."
Dr Anthony Seldon, master of fee-paying Wellington College, said: "The proposed changes to A-levels are a step in the right direction, in that it would be a move away from the mindless 'satnav' A-level towards a real test of the student's abilities and the exams would be much more likely to inspire challenging and thoughtful teaching.
"However, they are still some way short of the rigour, the breadth and the depth of the International Baccalaureate."
Brian Lightman, general secretary of the Association of School and College Leaders (ASCL), said: "We need a debate about the pros and cons of modular A-levels. It is simplistic to say that a course done in modules is easier than one with terminal exams. Nearly all university courses are modular and I have yet to hear criticism that they aren't rigorous enough.
"School and college leaders will be keen to keep AS-levels as they broaden the curriculum for young people. They give 16-year-olds more options as they start A-levels and allow them an additional year before they narrow down their choices at A2.
"Our biggest concern is the timescale. A deadline of September 2013 to have the new specifications ready means that, once decisions have been made, awarding bodies have very little time to work with universities to implement the changes.
"The last time there was a significant change to A-levels we saw major problems because there was not enough time allowed for the design and the changes were rushed. If this happens again it could cause problems for the exams in 2014."
Pam Tatlow, chief executive of university think-tank million+, said: "We welcome an opportunity for universities to be involved in developing A-levels.
"But A-levels are not core business for higher education. A co-ordinating body would be necessary to achieve the level of involvement with all exam boards that is envisaged by Ofqual.
"A-levels would lose all credibility for students, employers and higher education if their approval depended on a small sub-set of universities."