Rob Oakeshott, the sitting independent MP for the state seat of Port Macquarie, converted his enormous primary vote in NSW to win the federal seat, held by the Nationals - and its predecessor, the Country Party - since it was created almost 60 years ago.

The result marked another setback for the Nationals, who have been struggling on the increasingly urban NSW coast and have been reduced to nine federal seats.

The federal leader, Warren Truss, said the Nationals would reconsider their future after the weekend's election results in Lyne and in Western Australia.

"All of the options are on the table," Mr Truss said.

"We will certainly be looking at mergers but we will also be looking at the options of being more separate and doing the things we do now better.

"We have just had a marvellous result in Western Australia where a different approach has been taken, so we have to look very seriously at that."

Two months after the Nationals' gained a 6pc swing in a byelection to hold the seat of Gippsland, their candidate in Lyne, Rob Drew, suffered a 30pc swing on primary votes - the worst swing in a byelection in recorded history.

Labor did not contest the byelection.

The ABC's election analyst, Antony Green, said about half the population of the seat of Lyne was in the Port Macquarie area and it was no longer a rural seat.

Like many electorates on the northern NSW coast, an influx of city residents has increased support for Labor and the Greens.

"These seats are full of people who have never voted for the Nationals and then an MP retires and is replaced by a candidate they have never heard of," Mr Green said.

"Those people are up for grabs. The seat is dominated by the same issues you find in the outer suburbs of capital cities … as opposed to issues over retaining existing services that you find in rural areas."