Bill Shorten has insisted the runaway National Disability Insurance Scheme will be on a financially sustainable trajectory by February, when he will retire from politics to take up the role of vice chancellor of the University of Canberra.

Mr Shorten, 57, who led Labor to the 2016 and 2019 elections, has become the third cabinet minister to call it quits in the last six weeks, declaring he was tired of politics and had one more career left in him.