"We won't stand in the way of that," Senator Wong told the ABC's Insider's program on Sunday.

"We had deep concerns about the proposed tax hike when there was a suggestion it would hit people on $80,000 a year. Obviously we're pleased the government responded to that pressure [by lifting the rate at which it kicks in]."

Last week, Labor was still unsure about whether it would support the government's deficit tax on high income earners.

Shadow treasurer Chris Bowen signalled at the National Press Club on Wednesday that Labor was willing to negotiate on the issue.

"We will be as constructive as we can be on measures we don't find as unconscionable as the ones I've outlined," Mr Bowen said.