Deputy PM Warren Truss says his Nationals MPs are within their rights to cross the floor over the government’s parental leave scheme.

Deputy Prime Minister Warren Truss has raised the prospect of Nationals MPs and senators crossing the floor to vote against the government’s paid parental leave scheme.

The government is committed to having its scheme up and running by July 2015, even though Tuesday’s budget allocated $1.9 billion to continue Labor’s existing program.

The Greens have flagged support for the coalition scheme, almost certainly ensuring its passage through parliament.

But some Nationals have indicated they may vote against the proposed legislation.

“That’s a right, that’s a privilege that members of our party have,” Mr Truss told reporters in Brisbane on Wednesday, adding it was exercised very rarely.

The Nationals leader denied Prime Minister Tony Abbott had done a deal with the Greens.

“He made up his own mind that this was the right path to follow,” Mr Truss said, referring to Mr Abbott’s decision to lower the salary cap from $150,000 to $100,000.

“I’m delighted that the Greens agree with us.”