Poor leadership and management is a significant reason that 35 colleges were rated inadequate during the first four years of a new inspection regime, inspectors said this week.
There continues to be a small number of poorly managed colleges with "an ill-defined purpose, inadequate self-assessment arrangements, poor leadership, and weak teaching at the heart of institutional failure", said the inspectors in Further Education Matters, a report from the Office for Standards in Education.
David Bell, Ofsted's chief inspector, wrote: "Despite the evidence of increasing quality, it remains true that not all FE colleges are effectively led.
"There are powerful structural reasons why some colleges fall into inadequacy, but inept leadership and management are still too frequently contributory factors. It is equally a matter for concern that the judgement came, in many cases, as a surprise."
The report summarised the first cycle of inspections Ofsted carried out with the Adult Learning Inspectorate in which 424 colleges have been inspected since 2001.
It reveals that, of the 35 colleges that were rated inadequate, 17 remain so. No sixth-form college failed its inspection.
Outstanding leadership and management were found in 26 sixth-form colleges and 15 general further education colleges.
The report highlighted an "accelerating trend" of improvement in which success rates have risen and there is an increase in good and outstanding teaching.
It said: "The greatest achievement of the four years has been the reduction in the proportion of colleges which are inadequate from 11 per cent to just over 4 per cent. This would not have happened without a rigorous programme of re-inspection."
The chief inspector said he supported the view of Sir Andrew Foster that tough action should be taken against colleges that are slow to improve.
Sir Andrew last week called for colleges to be taken over by another college or another body if they fail to come up to standard by a given deadline.
Mr Bell added: "Overall, I am optimistic that FE colleges can rise to the challenge set for them by Sir Andrew.
"The success of our re-inspections of failing colleges and poorly performing curriculum areas shows how quickly colleges can turn themselves around when they have little alternative."
He stated that a lack of clarity over the way colleges are funded hindered improvement. He said: "Excessive complexity in funding arrangements is a significant constraint upon the ability of colleges to make desirable progress."
He listed other barriers to progress as excessively complex qualifications, the existence of too many bodies with an interest in quality, and performance measures that steer colleges away from much needed vocational courses.
"A college which offers a predominantly vocational curriculum risks being judged to be less successful because it will have a lower overall success rate than colleges which offer predominantly GCSE and A-levels," he added.
A second Ofsted report, on area-wide inspections, which examined strategies to raise achievement and recruit more 14 to 19-year-olds, revealed that one-third of the areas inspected were unsatisfactory.
The report said that in many areas, establishing a "joint vision" for 14-19 education and training has not been a strategic priority. It accused local education authorities and local learning and skills councils of often having "their own separate approaches, as do individual institutions, particularly colleges and schools with sixth forms".
Of the 30 14-19 area-wide inspections carried out, nine areas were rated good and just one was outstanding.