Top universities are drawing up blacklists of "soft" A-level subjects that will bar applicants from winning places on their degree courses.
They are warning that candidates who take more than one of the subjects such as accountancy, leisure studies and dance are unlikely to gain admission. They say they lack the academic rigour to prepare students for courses and are alarmed at the way increasing numbers of state schools are using them to boost pupils' top grades.
Disclosure of the lists will anger the parents of many pupils whose schools have failed to warn them that the A-level subjects are effectively worthless for entry to the best universities.
Ministers will also be concerned that they will undermine attempts to increase the number of state pupils at leading universities, traditionally dominated by independent schools.
Some universities such as the London School of Economics (LSE) and Cambridge University have already published lists of up to 25 subjects on their web-sites. Others are less overt but still operate lists.
Wendy Piatt, director-general of the Russell Group of 20 leading universities, said most top institutions would follow suit in "providing a steer on preferred combinations of A-levels".
She warned that a new analysis carried out by the group showed that a gulf was emerging between state and private schools, as comprehensives opted for "soft" A-levels and independents and grammars tightened their grip on traditional academic subjects.
"Clearly if pupils from state schools are increasingly taking a combination of subjects which put them at a disadvantage in competing for a course at a Russell Group university, the task of widening participation in our universities becomes even more difficult," said Piatt, a former deputy director of Tony Blair's Downing Street strategy unit.
The list run by Cambridge advises potential applicants against taking more than one from a list of 25 subjects ranging from business studies to dance and tourism. It warns that such a combination "would not normally be considered acceptable".
"Doing these A-levels individually is not a problem, it is doing too many of them," said Geoff Parks, director of admissions at Cambridge University. "We know there are bright students on track to get As but in subject combinations that essentially rule them out."
The LSE has named 10 subjects that it deems questionable. They include many of those named by Cambridge, but also others such as law. A spokes-woman for Oxford said that it did not operate a list but that candidates who opted for "meatier" A-levels were likely to gain some advantage.
The Russell Group findings are unlikely to please ministers, who have accused universities of failing to do enough to attract working-class students.
In September, John Denham, the universities secretary, called the current system a "huge waste of talent", adding that there was a "social bias" across higher education institutions, "including some of the most sought-after".
The Russell Group research shows the widening divergence between subjects being studied at different schools. In media studies, for example, 93% of pupils were from nonselective state schools, far above the sector's 74% share of all A-levels.
The situation is reversed in science, languages and maths. In the state sector, fewer than one in 10 A-level pupils in nonselective schools takes sciences, compared with one third at grammar and independent schools. In further maths, 35% of exams are taken at private schools, far above the sector's 15% share of all A-levels.
Meanwhile, the number of independent school candidates taking languages has remained steady, while those in the state sector have plummeted.
"It is overwhelmingly the state school students dropping sciences and languages," says the research. "This is making it increasingly difficult for the Russell Group to recruit large numbers of state school pupils into these difficult subjects."
The choice of subjects is increasing the dominance of independent and grammar school students already shown by their higher grades - the two groups together accounted for 52.3% of those gaining three As in 2006, although they made up only 21% of candidates.
Competition is becoming increasingly tough at the top universities, with 94% of the students who entered Cambridge last year securing more than three A grades at A-level. At Bristol, for example, there are 10 candidates for every place.
The Department for Children, Schools and Families said: "More young people are staying on at school taking A-levels and achieving - surely that's something we should welcome." ( Times )