Prime Minister Tony Abbott's scheme has been the subject of renewed criticism in the past week from Palmer United Party leader Clive Palmer, while some Nationals MPs, including Senator John Williams and George Christensen, have publicly questioned it.

In April, Mr Abbott scaled back the ambitious scheme, which as originally proposed would have paid a woman earning up to $150,000 her full replacement wage for six months.

The scheme has now been capped at $100,000, delivering a maximum payment of $50,000.

On Sunday, Mr Truss said the Nationals had committed to supporting the scheme and “it's therefore supported”.

“I accept that there are people in our party room and for that matter the Liberal party room who are not that keen on the scheme but I think there's been far, far too much emphasis placed on the high-income earners,” he told the ABC's Insiders.

“People in small business or on the farm that have got very small incomes, they will now be able to take a break from their small business or the farm to have the family because they will receive paid parental leave, which will be better than the amount that they're actually receiving in work at the present time.”

“I think that this scheme offers an enormous amount to people in small business, people on the farm, those earning comparatively low wages in country towns.”

Mr Truss also played down the fact that Mr Abbott will not meet the heads of the IMF and the World Bank before his visit to Washington and New York.

“I understand he's having a number of meetings with Treasury officials and others in the US,” he said.

“These programs are often pretty liquid and meetings are being arranged right down to the last minute. But [IMF chief} Christine Lagarde was in Australia not very long ago and had extensive consultations with people in Australia.”