One in five graduates earns less than a person who left school with as little as one A-level.
The official figures raise doubts that thousands of students have wasted their time with 'useless' degrees.
On average, the Office for National Statistics says that a person with a degree or higher academic qualification, such as a PhD, earns ￡16.10 an hour.
By comparison, a person who got at least one A level, or an equivalent qualification, typically earns ￡10 an hour.
But 20 percent of graduates earn less than ￡10 an hour, the amount they would have earned without a degree
The figure could be even worse in reality because the ONS did not include graduates who are unemployed or who have never worked.
The study also said the proportion of graduates doing low-skilled, badly-paid work has quadrupled to 2.3 percent since 1993. Many of these end up doing jobs which require little or no training such as hotel porter, postman, cleaner or catering assistant. Business groups have repeatedly warned that employers are turning their backs on graduates.
A recent report from the British Chambers of Commerce said too many graduates have 'fairly useless degrees in non-serious subjects'.
Phil McCabe from the Forum of Private Business said: 'The value of a degree is dwindling.'
Tanya de Grunwald, founder of Graduate Fog.co.uk, a website for job-seeking graduates, said many are devastated by the salaries they are offered.
She said: 'Finally, the figures from the ONS back up what our graduates have been saying – that they are just not getting the quality of job that they thought their degree would lead to.
'People say that a graduate typically earns ￡26,000, but this doesn't reflect the reality. Many of them are just scraping the barrel.'
One anonymous contributor to a student website wrote: 'If I could have my time back, I wouldn't have gone to university.
'I graduated last year and work in a friend's café for ￡6 an hour.'