The data shows that the total workforce shrank by 1.7 per cent between 2012-13 and 2013-14, with non-senior managers down 5.5 per cent and teachers down 0.7 per cent.
Teachers now account for a larger proportion of full-time staff in FE colleges, up from 43.5 per cent to 44.1 per cent, while the proportion of managers has decreased from 8.9 per cent to 7.6 per cent.
The figures also indicate that the average pay for FE teaching staff has fallen for the second year in a row to pound;29,400 - pound;247 less than in 2012-13. This compares with an average salary of pound;38,100 for schoolteachers. There is significant variation in pay across regions, with salaries highest in Greater London and lowest in the Midlands and East England.
Andrew Harden, head of further education at the University and College Union, said the apparent decrease in FE teachers' pay was not unexpected.
"When you consider the funding crisis in the FE sector, and the research we have carried out that shows an increase in the number of colleges not adhering to the agreed national pay scales, it's not surprising it has had the effect of lowering average pay," he added. "It is bad news not only for lecturers but also learners in colleges."
But Mr Harden said the survey results were undermined by the "questionable quality" of the data.
The information is based on analysis of data from the Staff Individualised Record, which is supplied by colleges on a voluntary basis. However, response rates have been declining, and for 2013-14 only 84 colleges - approximately a quarter of the total - supplied up-to-date information.
"Colleges in receipt of public funds should have a statutory obligation to reply [to the survey]," Mr Harden said. "Because so few colleges have replied, we don't have the high-quality data to back up the arguments we are making about the effect of austerity on the sector."
The FE workforce is also getting older: the data shows that the mean age of all staff has increased from 44 to 45, with the proportion of staff aged 60 and above increasing from 11.7 per cent to 13.4 per cent.
Carol Jones, chair of the corporation of Stoke on Trent College and a national leader of governance for the ETF, said the report should prompt colleges to consider whether they have the right skills for the future.
"Do we have the right profile of staff in the right roles to achieve our strategic ambitions?" she asked. "Are we creating new roles fit for the future? How is the shape of our college workforce changing to manage the challenges we are facing across the sector?"
Over the next 18 months, the ETF is planning to change the way it collects and publishes workforce data to make it more useful for colleges. The body wants leaders and governors to be able to use it as part of their annual planning.
Chief executive David Russell has appealed for more organisations to contribute to the process to improve the quality of data available.
"With sector-wide commitment to data collection, we can identify specific issues and support smart, sector-wide solutions," he said. "Without provider support on data collection we are all in the dark."
`A more professional workforce'
An Education and Training Foundation report on work-based learning organisations shows that the proportion of teaching staff employed in the sector has risen from 48 per cent in 2011-12 to 53 per cent in 2013-14.
However, the proportion of staff holding a teaching qualification has fallen from 80 per cent in 2012-13 to 61 per cent, although the researchers note that making comparisons is difficult owing to the number of organisations taking part in the survey for the first time.
The report finds that the work-based learning sector is still struggling to recruit teaching staff in functional skills, maths and English.
Apprenticeships are key for most providers, with 82 per cent offering 16-18 apprenticeships and the same percentage offering 19-24 apprenticeships.
Stewart Segal, chief executive of the Association of Employment and Learning Providers, says: "These figures confirm what we thought: that over the last few years more work-based learning providers have been working towards a more professional workforce.
"English and maths are key areas where we need to continue that professionalisation."