Nationals Senator John Williams has urged Prime Minister Tony Abbott to put his paid parental leave scheme on ice and adopt a compromise proposal to avoid a showdown with MPs unhappy about the generous proposal.

The paid parental leave scheme is deeply unpopular in some sections of the Coalition and Senator Williams, along with senators Dean Smith, Cory Bernardi, Ian Macdonald and Ron Boswell and MP Alex Hawke, have publicly flagged concerns about the policy.

Privately, some Coalition MPs are considering crossing the floor to vote against the proposal, which would pay women their full replacement wage for 26 weeks, capped at a maximum payment of $50,000 and which also includes superannuation payments.

Mr Abbott watered down his original proposal, which would have cost up to $5.5 billion annually and delivered a maximum payment of $75,000, in April. The current scheme introduced by Labor cost $1.7 billion annually, offers 18 weeks pay at the minimum wage of $622 per week but no superannuation.

Senator Williams told Fairfax Media the Prime Minister needed to go further to win over opponents in the party room and suggested extending Labor's scheme.

"Perhaps a compromise would be extending the minimum wage payment from 18 to 26 weeks, plus super," he said.

"Then when the economy is stronger and the budget is balanced and we are not borrowing any more money we can bring in the more generous scheme. That would be a sensible compromise."

But Mr Abbott on Monday said he was sticking by his policy.

Speaking to reporters in Canada, the Prime Minister appeared to misunderstand where the opposition to his scheme was coming from, saying the government would deal cordially with crossbenchers in the Senate on the policy, but warned he expected the government's mandate to be respected.

''Let's not forget that this is a policy we took not to one but to two elections and let's not forget that this is fundamentally a matter of justice for the women of our country, for the mothers and for the parents of our country,'' he said at a media conference.

''Why should people be paid at their real wage when they go on holidays, when they take long service leave, when they have sick leave and then be paid effectively a welfare wage when they go on parental leave?

''It just doesn't make sense and it is my fundamental conviction that parental leave is not a welfare entitlement, it's a workplace entitlement, and that's why I'm sticking with the policy we've got.''

Senator Williams would not be drawn on whether he would cross the floor and vote against the scheme if was not amended, saying he would "look at it when it comes to the Senate" and signalling more needed to be done for farmers.

Western Australian Senator Dean Smith declined to comment on Senator Williams' proposal but said he continued to have "great reservations" about the current policy.

Senator Bernardi and Senator Boswell both declined to comment on the policy.

The government has not set a date for the scheme to be brought to the Senate for a vote.

But even if the government can secure the support of the Greens in the current Senate, just five Coalition MPs would need to defect to defeat the bill.

And the task will be no easier in the new senate, with Palmer United Party leader Clive Palmer having also spoken out against the policy

On Sunday, Deputy Prime Minister Warren Truss admitted the policy was not popular in the Coalition party room but insisted it offered benefits to small businesses and farmers.

''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.

Mr Abbott on Monday also issued a warning to two incoming crossbench, Family First's Bob Day and Liberal Democrat David Leyonhjelm, who reports say are planning to oppose the government's bid to dump Labor's final round of income tax cuts, which were part of compensation for the carbon tax.

''The Liberal Democrats will never vote for an increase in taxes and, therefore, we won't vote to reverse a tax cut,'' Mr Leyonhjelm told The Australian.

Mr Abbott said he'd like nothing more than to be able to give another ''swift round of tax cuts'' but the fiscal position made that difficult.

''Obviously we're going to talk respectfully to the crossbench senators,'' he told reporters in Ottawa, Canada. ''But we also expect them to respect the fact the government has a job to do . . . to bring the budget back under control as well as to repeal the carbon tax.''

Without the carbon tax there was ''much less need'' for associated compensation, he said. The tax-free threshold has already increased from $6000 to $18,200 and Labor planned to further lift it to $19,400 as part of its carbon tax compensation.

Meanwhile, Opposition Leader Bill Shorten will capitalise on Prime Minister Tony Abbott's absence overseas and launch a blitz of marginal seats to highlight the broken promises in the budget that will push up the costs of living for families.

In a sign of Labor's growing confidence following an extraordinary budget backlash, Mr Shorten will visit marginal seats in Melbourne, Sydney and Brisbane.

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