Schools and colleges should mount a "bottom-up" campaign to restructure England's exams system, academics say.
Ken Spours said many students found GCSEs boring
Earlier this year ministers turned down proposals for a unified diploma for 14 to 19-year-olds, covering both academic and vocational subjects.
But London's Institute of Education says GCSEs are "boring", "off-putting" and add to a high drop-out rate at 16.
It wants local authorities to set up their own diploma programmes, to add to "pressure" on central government.
'In for distance'
Ken Spours, an IoE academic, told a conference in London: "We need to start building from the bottom, not just the top.
"We are here for the distance and we are not giving up now. What we are calling is needed in practical terms.
"This is about real learning experiences and learning opportunities for young people."
Plans for 14 to 19 education, put forward by former chief schools inspector Sir Mike Tomlinson, had promised greater continuity between stages.
The diploma was to take in academic and vocational learning.
Sir Mike also advocated more working together by schools and colleges to create more variety for pupils. In its response, the government promised a diploma specifically for work-related subjects, to raise their status.
However, it said it would keep separate GCSEs and A-levels.
Dr Spours, a former member of Sir Mike's working group, said too many students thought they were not going to achieve five A* to C grades at GCSE, nowadays the "benchmark" asked of them.
He added: "If it's boring and you are going to fail, then no wonder you are going to walk away."
The Tomlinson diploma plans envisaged every successful candidate proving competence in maths, English and information technology.
In response, the government wants every pupils listed as having "passed" five GCSEs to have done so in maths and English.
This, it says, will make school performance tables more meaningful.
But, according to Dr Spours, it will lead to fewer children achieving the "benchmark".
His colleague, Ann Hodgson, said schools across boroughs should work together to provide their own diplomas, combining GCSEs, A-levels and vocational work.
Dr Hodgson said: "Children would actually have a core of learning."
The diplomas could form a record to be used for moving between school and college.
If they extended beyond the local level, to become London-wide for instance, they would be noticed by universities.
Dr Hodgson said she was "deeply disappointed" by the government's decision not to accept the Tomlinson proposals wholesale, adding: "Many schools are already doing work in that direction.
"If we keep going on like this, there is the political will in the profession to extend it further."
The Liberal Democrats have said they would establish a "climbing frame of learning" in which pupils could mix academic and skills-based courses, and replace GCSE, A-level and vocational qualifications with a diploma system.
The Conservatives would keep GCSEs and A-levels, restricting top A-level grades to a fixed percentage of students each year, and let schools offer O-levels.