Nearly a third of pupils aged 14 and above say they have received no careers guidance from their school or college despite a new youth service costing pound;441 million a year.
Connexions was set up three years ago to bring together services for young people aged 14 to 19 and to provide better careers advice.
Ordinary pupils were missing out because the service was trying to meet targets for working with their disaffected peers, the National Association of Careers and Guidance Teachers said.
Its comments followed a survey of 500 14 to 19-year-olds in England, Scotland and Wales by pollsters NOP World.
The survey found that even among 16 to 19-year-olds, as many as 21 per cent had no careers help.
Schools have a statutory duty to provide careers advice to all pupils in Years 9 to 11. From September, that requirement is to be extended to Years 7 and 8.
One sixth-former said: "Careers advice is only really used for work experience; (it's) not seen as a priority."
The poll for businessdynamics, a business education charity, also found that where pupils did have access to guidance, the experience was a good one - 87 per cent reported that they were satisfied or very satisfied with the advice given.
Sylvia Thomson, president of the 2,000-member National Association of Careers and Guidance Teachers, said the figure of 30 per cent failing to get advice was not a surprise.
She said Connexions had been given performance targets for working with socially excluded young people. As a result, resources were not being invested in giving advice to "run-of-the-mill pupils".
Ms Thomson added: "Because schools are under so many pressures as far as curriculum time goes, it's very difficult for some to lay on the careers advice lessons they should be providing.
"Teachers will often need to undertake in-service training. I don't think that there's evidence of malpractice on the part of schools, but at the moment they are finding they have more urgent priorities."
The NACGT is writing to ministers calling for a review of guidance arrangements. It wants prospective secondary teachers to receive better preparation for careers advice during their initial training and a greater place for guidance in the core curriculum.
Good guidance for youngsters is assuming increasing importance as ministers try to enhance pupils' choice of courses under proposals to improve vocational options for 14 to 19-year-olds.
David Millar, chief executive of businessdynamics, described the survey's findings as "disturbing", especially because it also found that youngsters viewed business, industry and commerce "stereotypically".
Frequent words used to describe businesses were "Filofax", "stressed" and "briefcases", while some youngsters summed up commerce as "geeky" and "drinking lots of coffee and smoking a lot".