Treasurer opposed 15pc tax deal: Hinch

Key crossbench senator Derryn Hinch says Scott Morrison had told him of concerns about a 15 per cent backpacker tax rate hours before the announcement.

Treasurer Scott Morrison told a Senate crossbencher a 15 per cent backpacker tax rate would cost the budget "too much money" just hours before relenting on the change.

Independent senator Derryn Hinch said Mr Morrison had made the comment at a party hosted by the prime minister on Sunday night.

"(Mr Morrison) said it would cost too much money if it dropped to 15, but something obviously happened in the interim, so they have," Senator Hinch said in Canberra on Monday.