The figures were revealed in an audit produced by the University of Greenwich for Focus, the Central London Training and Enterprise Council.
The number of students enrolled on FE courses in London almost equals the number attending secondary schools. However, the vast majority - 65 per cent - are part-time. Half the students are on courses at level 1 - equivalent to a GCSE grade A-G - or introductory courses which are not graded.
Many Londoners take general education courses: basic education, computer literacy, word processing and English for speakers of other languages.
These courses are mainly outside the national qualifications framework, but, says the research, each category involves as many or more students as those taking A-levels, BTEC, City amp; Guilds or vocational qualifications.
"If FE can be said to have a curriculum, then it is a chaotic one. Londoners are studying in colleges for 2,773 qualifications awarded by 229 bodies," says the report by Judith Watson and Emma Williams, at the Learning Policy Unit, University of Greenwich.
The awarding bodies range from the Arboricultural Association to the Yorkshire and Humberside Association for Further and Higher Education, the International Health and Beauty Council and the Register of Approved Driving Instructors.
In the capital, 56 per cent of the young people who stay on in education go to college, 6 percentage points more than in England as a whole. Of 17-year-olds still in education, 64 per cent are in college.
FE students in London were as likely to drop out as those elsewhere in England.
Sixteen-year-olds were twice as likely as adults to drop out of courses, 32 per cent withdrew during the course of a year. Many students do not drop out of college totally, but reduce the number of subjects that they are taking.
The pass rate in London colleges was only 50 per cent, compared to an English average of 65 per cent.
"Further education in the capital is complex and in many ways incoherent. It tends to become the residue - everyone who is not in school, higher education or work-based training. This is both its strength and weakness.
"It is more flexible and responsive than other educational sectors, but it does not always know where its priorities lie."