Schools will be freed from the responsibility to make all Diplomas available to pupils under Tory plans to overhaul the Government's flagship qualifications.
Under current rules, schools will be forced to work in partnerships to make all 17 Diplomas available at three levels.
But the entitlement for pupils to access the 51 "strands" will be cut by the Conservatives, who expanded on their plans at last week's Specialist Schools and Academies Trust conference in Birmingham.
The Tories have already said they would scrap the planned introduction of academic Diplomas in science, languages and the humanities, due to begin in 2011.
But Nick Gibb, shadow schools minister, said it would be for schools to decide which vocational Diplomas they want to offer.
"Academic Diplomas replicate what GCSEs and A-levels provide, so they will not continue under us," he said.
"As for the vocational Diplomas, we want them to succeed but we are concerned that they are neither one thing nor the other, neither academic nor vocational. We will not require all schools to offer all 51 strands. The logistics of that in schools is becoming a nightmare."
Mr Gibb told delegates he knew of schools forced to radically alter their timetables to fit in Diplomas.
"We shouldn't be changing our pedagogical approach to teaching just to fit in with some very complex logistical timetable," he said. "It should be your own choice. The jury is still out on them. We want (the courses) to work, but we want them to work more practically."
He said schools may choose to specalise in one Diploma and "blow their trumpet" about that. It is understood the Tories had previously considered abandoning Diplomas completely, despite the #163;295 million that will have been invested by next March.
Ed Balls, Schools Secretary, has said Diplomas could become the qualification "of choice" for teenagers. But their popularity has failed to live up to expectation. Only 12,072 people signed up to the 14-19 Diplomas in 2008-09, far fewer than had been hoped.
Removing the need for schools to make all Diploma strands available to all pupils was welcomed by John Dunford, general secretary of the Association of School and College Leaders.
"The opportunities for young people in areas where there is strong collaboration have increased immensely," he said. "But the obligation to offer every Diploma at three levels to all pupils by 2013 is a major stumbling block.
"In rural areas, it is an impossibility. Even in the tightest-knit of urban areas, the logistics are a nightmare scenario."