The Government has warned universities against setting up new foundation courses and filling them with students who have failed their A levels.
Gillian Shephard, Secretary of State for Education and Employment, said she would "strongly resist" moves to extend the practice of offering foundation programmes as "a matter of routine" to students with poor entry qualifications.
Launching an inquiry into A level, GCSE and higher education admissions standards, Mrs Shephard said she had been concerned by reports that some universities were enrolling students with no A levels on foundation courses in pre-paration for degree programmes.
"What I am not in favour of is foundation courses which ignore the intellectual capacity of the candidate to achieve a university degree. No A level passes does not seem to me like the right kind of intellectual capacity," she said.
Mrs Shephard has called on the Higher Education Quality Council to take a close look at the number and type of students being admitted on to foundation courses.
The move follows news this week that 4,081 students have so far been admitted to higher education through clearing, compared to just 2,870 at this time last year.
But Tony Higgins, chief executive of the Universities and Colleges Admissions Service, said this was not an indication that admissions standards were falling.
"These days we recognise that people develop at different speeds, and their performance at A level is not necessarily an accurate indication of their likely performance in higher education," he said.
Peter Williams, director of quality assurance for HEQC, said there were many questions to be asked about the purpose of foundation courses. But he added: "It is not fair to equate the entry qualifications for foundation courses to those for a degree programme."
Mrs Shephard has also instructed the Schools Curriculum Assessment Authority and the Office for Standards in Education to carry out a study of A level and GSCE standards in the light of higher grades awarded to students this year.
The study will analyse examination results over the past 20 years, and its conclusions, expected by the end of March, will feed into Sir Ron Dearing's review of qualifications for 16 to 19-year-olds.
Mrs Shephard said she was encouraged by the fact that there had been "modest" increases this year in the number of students passing A levels and achieving higher grades. But she was concerned to ensure that rigour was not being diluted.
"We need to be sure that A levels are still delivering the goods. I have no evidence that there are grounds for concern, but too much has been invested to leave things to chance."