The exam board with the biggest share of the Diploma has called for it to be simplified after figures showed that a disappointingly small number of pupils completed the qualification this year.
Only 3,069 pupils were awarded a full Higher Diploma - judged equivalent to GCSEs - this summer.
Ziggy Liaquat, managing director of the Edexcel exam board, accepted the numbers were "much lower" than original estimates and blamed its complexity, saying a simplification was "critically important".
The applied-learning qualification developed by the last Labour government to rival GCSEs and A-levels requires pupils to complete several elements, including a core "principal learning project", functional skills in English, mathematics and ICT, work experience, an extended project and personal, learning and thinking skills.
Mr Liaquat said: "Teachers and students say the principal learning project has real value and is a strong part of the qualification offer. However, it's clear the completion rates are low, which is a result of the Diploma's complex nature. We'd call for a simplification of the structure of the Diploma to take some administrative burden off the system, which doesn't have a great deal of value. Simplification is critically important."
John Dunford, general secretary of the Association of School and College Leaders (ASCL), said the numbers completing the Diploma were "encouraging".
"More will finish the components for the qualification and achieve the Diploma over the coming months," he said. "It's important to recognise that students have not failed if they have not yet passed every component by age 16."
Nick Gibb, schools minister, said: "There will be a place for the Diploma as long as there is demand for it."
3,069 - Number of pupils awarded a full Higher Diploma this summer.