Inspectors this week put forward three reasons why a "striking" north-south divide has emerged in the performance of general further education colleges.
Ofsted revealed that one college in five in the south of England has been rated inadequate, compared with one in 20 in the North.
It said colleges in the South face greater competition, are less skilled at understanding the vocational mission of colleges, and find it harder to recruit staff.
David Bell, Ofsted's chief inspector, said: "Almost all the colleges in the South are in areas where there is very intensive competition among post-16 providers and where the general further education college is often the institution of last resort, particularly for school-leavers.
"A general further education college's intake is non-selective and increasingly they are catering for students whose previous academic achievements have been minimal because their education has been fragmented or largely non-existent.
"Almost without exception, inadequate colleges have too few teaching staff able to deal with the particular challenges that such students bring."
He added: "It is possible that colleges in the North have a greater understanding of how to educate and train the artisans of the 21st century because they are rooted in the industrial heartland of the country."
FE Focus revealed last week that of the 11 GFE colleges rated inadequate in the 2003-4 academic year, only one, the People's college in Nottingham, was north of Birmingham.
Now Ofsted has detailed its reasons why the north-south divide exists in two reports, Why colleges succeed and Why colleges fail.
The reports analyse inspections carried out in the first three years since Ofsted and the Adult Learning Inspectorate, took over college inspections from the Further Education Funding Council.
In that time, 307 GFE, tertiary, sixth-form colleges and specialist institutions such as agricultural and performing arts colleges were inspected, of which 37 were rated inadequate, a failure rate of 12 per cent.
No sixth-form college was rated inadequate, and 29 of the failing colleges were GFE colleges. Of the 37 inadequate colleges in total, 29 are to the south of Birmingham.
Mr Bell said: "Inadequate colleges tend to forget that their function is to teach young people and adults important vocational and life skills. But the educational mission of these colleges is often vague, or non-existent.
"They refer to inclusion or extending participation, oblivious of the fact that inclusion in failure and participation, irrespective of quality, benefits no one."
Why colleges fail said that most inadequate colleges "have responded with alacrity to the exhortation to widen participation without understanding that under-represented groups deserve better than to be enticed back into education to fail again".
It added: "The general inability of such colleges to focus primarily on outcomes for learners as opposed to processes and procedures has poorly served many young people and, occasionally, a large number of adults returning to education.
"Given the competitive post-16 educational climate, surprisingly few have understood and developed a primarily vocational portfolio which fills a distinct market niche.
"It takes a failure at inspection for these colleges to review and revise their 'free for all' approach to recruitment and to consider abandoning those academic courses at which their competitors, with their selective entry, are inevitably more successful."
The third reason given was the difficulties in recruiting college staff in the South, especially in London and the home counties, where house prices are high.
The reports said: "Recently qualified teachers cannot afford to take up posts offered. Nor can experienced teachers from successful colleges elsewhere in the country be persuaded to join the staff.
"The workforce is therefore an ageing and static one, often unable to cope with the requirements of new and demanding groups of learners and unenthusiastic about taking up in-service training that might be on offer.
"In relation to the differential between their pay and that of school teachers, they feel undervalued. Morale in such institutions is often low."
The other report, Why colleges succeed, said that a common feature of colleges rated outstanding is "a clear understanding of the parameters and potential of their assigned role".
Of the 29 colleges judged outstanding, 17 are sixth-form colleges, nine are general FE or tertiary and three are specialist colleges.
"They know exactly what they are there for, what they can provide well, which students they need to work with, what they have to do to ensure success and then judge critically what they have achieved," said the report.
It added that: "They understand the importance of investing in qualified specialist staff to whom they give ample opportunities for continuous professional development."
Mr Bell said: "The reasons for the success of these 29 colleges are, despite their different roles and locations, very similar. All have a clear understanding of the particular nature of their mission and pursue its realisation single-mindedly.
"Many of the outstanding colleges have an exemplary response to educational and social inclusion, understanding that equality and equity are not about empty rhetoric and glossy policy documents, but about practical action which results in success for their learners."