Four out of five parents do not understand enough about Diplomas to give advice to their children on whether to opt for the qualification.
Parents are unsure about the range of exams on offer
A survey for an education project in Yorkshire found great uncertainty among parents about vocational exams.
The study for the South Yorkshire Education Project found widespread confusion about the variety of qualifications on offer.
The first Diplomas are set to be introduced from September.
The organisation behind the survey is intended to raise awareness in South Yorkshire of the educational opportunities available - but it found that many families were struggling to make sense of the number of different options.
Vocational qualifications in particular seemed to baffle parents - with 35% saying they knew about NVQs, 27% saying they understood the concept of apprenticeships and 21% recognising BTECs.
However the least familiar qualification was the Diploma, which was familiar to 19%, suggests the survey of 600 people by ICM.
The new qualification is intended to bridge the divide between academic and vocational qualifications.
Last week at a head teachers' conference there were calls from senior school staff for a more simplified exam system - with warnings that teachers, parents and students were in a state of confusion over what the Diploma would offer.
In contrast, there was a much wider recognition for the academic qualifications - with 77% familiar with GCSEs and 57% feeling confident about understanding A and AS-levels.
Alison Firth, from the South Yorkshire Education Project, said the range of options available presented a challenge for parents.
The South Yorkshire Education Project is supported by the European Social Fund and European Regional Development Fund, local authorities and the Learning and Skills Council.
It has developed a website - Voced - to inform parents and students about 14-19 qualification options.
ICM conducted online interviews with a random sample of 602 UK parents with children aged 18 or under between the 14th and 16th of March.