Nearly a quarter of UK engineering graduates are working in non-graduate jobs or unskilled work such as waiting and shop work, a report suggests.
The study says it is "not easy or automatic" for qualified engineers to find related employment in the UK.
Employers and industry leaders have repeatedly raised concerns about a lack of good quality science and engineering graduates.
But research from Birmingham University research challenges this viewpoint.
The report - entitled Is there a shortage of scientists? - is being presented to the British Educational Research Association (Bera) annual conference in London on Thursday.
It analysed figures from 1986 to 2009 from the Higher Education Statistical Agency on the proportions of engineering students entering related jobs, other professions or work that did not require a degree in 2009.
The findings suggest that less than half (about 46%) of 2009 engineering graduates were in jobs directly related to their degree subject six months after leaving university.
About one in five (20%) were employed in roles that were not directly related to their degree and about one in four (24%) were in "non-graduate" employment, for example working as waiters or in shops.
The report says: "Perhaps, because of recent initiatives, there seem to be too many people studying science for the labour market to cope with, or perhaps graduates are no longer of sufficient quality.
"It is more likely, however, that all of these scientists are without relevant employment every year because the shortage thesis is wrong and there are no jobs waiting for all of them or because they are 'dropping out' having learnt that they do not enjoy their subject areas."
The report also suggests attempts to encourage more people to study science, technology, engineering and maths ("Stem subjects") have not proven successful.
Its analysis of long-term patterns of subject take-up shows that none of the three science A-level subjects has grown alongside increased post-16 participation rates.
"The number of young people continuing to post-16 education generally has risen since 1961 in the UK, but this has made little difference to the overall number taking physics, chemistry and biology," it says.
"Instead the picture shows the sciences largely competing among themselves for approximately the same total of students each year.
"The number of young people studying physics was lower in 2009 than in 1961 but was compensated for, if that is the right term, by an increase in numbers studying biology."
Report author Professor Emma Smith added: "It is astonishing, in the light of claims of science graduate shortages, that so few new graduates go into related employment.
"The figures suggest it is not easy or automatic for qualified engineers to get related employment in the UK, despite the purported shortages."
But the CBI, which represents British businesses, said employers still complained of a shortage of suitably qualified and employable candidates.
The CBI's director for education and skills policy, Susan Anderson, said: "The latest CBI survey shows that the shortage of science, technology, engineering and maths graduates is an issue for businesses, but companies also raised questions about the quality of Stem graduates coming through, many of whom were lacking in practical workplace experience or employability skills.
"It's crucial for graduates of all disciplines to do work experience and develop skills like team-working and self-management to have the best possible chance of finding a job."
Paul Jackson, Chief Executive of Engineering UK said there were skills shortages in some areas, such as power engineering, petrochemicals and systems engineering and talented students should not be put off by the research.
And Philip Greenish, Chief Executive of the Royal Academy of Engineering said: "Engineers are highly skilled professionals. Employers recruit them from wherever they can in a global marketplace. Only a proportion will be fresh UK graduates.
"To infer that employers don't know their own workforce needs when they identify a shortage of engineers, and to do this based on data that only considers a subset of recruits is just plain wrong."
Professor Nigel Seaton, senior deputy vice-chancellor at the University of Surrey and a chartered chemical engineer, said engineering degrees were often undervalued.
"They are good degrees to have, and equip students for a wide range of jobs. While many students embark on an engineering career, others thrive in a range of jobs, for example in management or finance."