The Abbott government should delay extending public funding to private colleges for at least three years because of concerns about shonky operators, the TAFE sector says.

TAFES previously supported the government's proposal to extend Commonwealth support to students at private colleges, TAFES, sub-bachelor degrees and diploma programs as well as university students from 2016.

TAFE Directors Australia, which represents 59 TAFE institutes, has now changed its position and is lobbying Senate crossbenchers to block public funding to for-profit colleges until concerns about the regulation of the sector are resolved.

The turbulence at education firm Vocation, which was recently stripped of $20 million funding by the Victorian government, meant a delay was required, TAFE Directors Australia chief executive Martin Riordan said.