University graduates taking home as little as $730 a week will have to start repaying their student loans from Sunday after the Turnbull government clinched a deal to claw back $250 million in higher education debt.

The bill debated in the Senate on Tuesday requires graduates to repay at least 1 per cent of their income once they start earning $45,000 a year, reducing the threshold from about $56,000.

It will also impose a lifetime cap on taxpayer loans of $104,440 for most students, but this will now be replenishable, after the government agreed to changes urged by its own members. This means students who reach the cap can access new loans once they pay down their debt.

Education Minister Simon Birmingham, right, talks with members of the crossbench. Credit:Alex Ellinghausen

Senator Stirling Griff of the Centre Alliance - formerly the Nick Xenophon Team - confirmed his party supported the crackdown, which was also backed by One Nation and key crossbenchers.