The poll of more than 250 UK managers found that 50% now rely on their firms' internal assessment tests - rather than exam results - to select employees.

A majority of those questioned by the Institute of Management said school leavers lacked determination, ambition and a willingness to work hard.

And many were concerned that GCSE results reveal little about a job applicant's suitability for work, with only four out of 10 saying they believed the exams were a reliable indicator of knowledge.

The survey's findings are published as students across England and Wales receive their GCSE results.

The Director General of the institute, Mary Chapman, said: "As the UK economy becomes increasingly services-led, school leavers need the right mix of skills to work successfully with colleagues and customers."

The Confederation of British Industry believes this year's rise in the number of young people taking GCSEs is a good sign, but that there is scope for improvement in the results.

'Grade inflation'

Its Director of Education and Training, Tony Webb, said the number of entries for physics and chemistry halted a "worrying decline" which was a good sign for the future.

"The critical issue for the future is not just whether GCSE standards are rising or falling, it is also about raising expectations."

The Institute of Directors says the modest increase in the higher-grade pass rate could be a welcome sign that "grade inflation" is coming to an end.

But it is concerned about the increase in exam failures, especially in maths and English.

The institute's Head of Policy, Ruth Lea, said: "While we are encouraged by signs that grade inflation may be moderating, there are far too many signs that schools are failing their pupils in the most basic subjects of maths and English.

"This, combined with the evidence of fewer graduates entering teaching, augurs badly for the future employability of school leavers."