The Weekend Australian newspaper said Nationals' polling places Mr Barilaro ahead of Labor leader Anthony Albanese's preferred candidate, Kristy McBain, at 52-48 per cent on a two party preferred basis.

Ms McBain is the mayor of Bega.

A date for the by-election, caused by the resignation of Labor's Mike Kelly due to ill health, has yet to be set.

In an email to party members, ALP national secretary Paul Erickson said the leaked polling confirms Labor has a fight on its hands.

"Our opponents will throw everything they've got at the by-election," he says, calling for donations.

"They will call on their big donor mates to flood the electorate with advertising as soon as the starting gun is fired."

Mr Erickson said this campaign won't be like ones that have been run in the past.

"Because of the coronavirus crisis, we don't know when the by-election will be and we might not be able to rely on our traditional field campaigning," he said.

"We need to be ready for a long campaign where digital, radio and TV advertising will be key to reaching the voters we need to."

News Corp newspapers also reported another potential contender from the NSW state government, Transport Minister Andrew Constance, has told the Liberal State Executive he will not run should Mr Barilaro choose to stand.

Australian Associated Press