It is costing taxpayers on average seven times more to educate a student at a private vocational college than a public TAFE, according to new analysis of federal government figures.

Taxpayers forked out $73,200 per graduate from private colleges on average, but only $10,500 per graduate in TAFE courses in 2014, two years after the Gillard government paved the way to marketise vocational training.

The analysis, done by the NSW Greens based on the federal Department of Education and Training's funding figures and the number of vocational graduates in 2014, comes in the wake of several scandals in the private vocational sector in which dodgy providers have been exposed allegedly recruiting vulnerable people into government-funded courses they had little hope of completing by giving them laptops or iPads.

In one case, the Sydney-based AIPE, a Senate committee heard the college received $111 million in Commonwealth funding after handing out just 117 diplomas in 2014.