Teacher awareness of 14-19 diplomas has failed to improve since 2007, with 43 per cent still saying they know nothing or not very much about the Government's flagship vocational qualification.
The findings, from a poll commissioned by Ofqual, the exam regulator, are bad news for ministers desperate to build confidence in the new qualifications, which suffered an underwhelming introduction to schools and colleges last September.
The Ipsos Mori survey, conducted last November and December, found that awareness about diplomas had declined among parents. Only 26 per cent said they knew a great deal or a fair amount about them - down from 32 per cent in 2007.
But there was an improvement in understanding among pupils, with those saying they knew a great deal or a fair amount about diplomas increasing from 35 to 39 per cent over the same period.
The news comes only a fortnight after the science diploma was described as a "slightly schizophrenic" concept by one of the Government's most senior education civil servant.
"Do we really know what we are about?" Professor Adrian Smith, director general of science and research at the Department for Innovation Universities and Skills, asked about diplomas. "Might we not be better getting GCSEs and A-levels right first?"
In September only 12,000 students signed up to the first diplomas, well below the 50,000 hoped for by the Government.
But the survey revealed better news for the Government on GCSEs and A-levels, with support for the established qualifications remaining high. Among teachers, incorrect grading of A-levels was a concern for 17 per cent, but overall confidence in the qualification had risen, with 38 per cent saying they had no concerns about it compared with 26 per cent in 2006.
Kathleen Tattersall, chair of Ofqual, conceded that there was still work to be done in building confidence in GCSEs and A-levels.
"The fact that fewer teachers felt the quality of A-level marking had decreased in the past two years is promising, although I recognise that a number of teachers continue to have concerns about the overall quality of marking," she said.
There are signs that the demands placed on A-level students are no longer increasing, with only a third of teachers agreeing that most work harder today than ever before. Before 2006, teachers were much more likely to take that view.
About three-quarters of teachers said they had confidence in both A-levels and GCSEs. On GCSEs, 83 per cent of teachers thought most or all pupils got the right grade, but only two-thirds of the general public agreed.
The previous survey was carried out in November 2007.