This is despite his public clashes with three Nationals senators in the past, most recently with Senator Ron Boswell.

"That was just a bit of colour and movement," Senator Heffernan said yesterday.

He supported mergers between the Nationals and Liberals, saying it was a "very strategic thing to do".

At their federal council meeting in Canberra at the weekend, National Party leaders touted the merits of the merger between the Liberals and Nationals in Queensland.

There was a spirited debate behind closed doors about amalgamation at the federal level and this was ruled out in the short term.

But Senator Heffernan said he was hopeful the Liberals and Nationals would move quickly to merge in NSW.

When queried about one at the federal level, he said it was "stupid to think that you can quarantine a constituency".

"We've got to get city people to understand country issues, country people to understand city issues and I enjoy a bit of colour and movement," he said.

But Senator Heffernan rejected suggestions there were tensions in the Coalition ranks.

Last week, Senator Heffernan and Senator Boswell clashed over the outcome in the Port Macquarie by-election, in which Independent Pete Besseling beat the Nationals candidate.

NSW National leader Andrew Stoner suggested federal Liberal MP Alby Schultz should be "marched out at dawn, blindfolded and shot" after it emerged that Mr Schultz had campaigned for the Independent candidate.

Mr Schultz said he had made a 30-minute visit to the electorate on NSW's mid-North Coast to support Mr Besseling because he had "great respect" for the candidate.

Mr Stoner went on to dismiss the comments as a throwaway line, but Mr Schultz called it a "vicious attack".

Tempers flared in Senate estimates when Senator Boswell and Senator Heffernan had a spat over the by-election.

Senator Boswell warned his colleague that "you start picking on the National Party and you'll get it back in trucks".