Ms Abbott, a long-time Scone resident who has been on the council since 2016, was described by the Greens as a passionate community campaigner who has been vocal in retaining local services and protecting the environment.

The Greens say she is also focused on protecting TAFE.

"The people of the Upper Hunter have been grossly let down by the major parties who seem to be competing with each other to lower the standard of politics, and this by-election is a great chance for locals to vote for change," Ms Abbott said.

"I am committed to protecting the Upper Hunter's air quality, farmland and water resources from the further expansion of the coal industry.

"Politicians need to be honest about the future of fossil fuels, the key driver of climate change and extreme weather events. This is an industry without a long-term future and we need policies to help map out a prosperous and healthy post-coal future for the Upper Hunter.

"Any expansion of coal, gas or gas pipelines in the Upper Hunter electorate will hamper the diversification of the economy and lock the Hunter into a dead-end future."

Greens MP David Shoebridge said Ms Abbott was "principled and passionate".

"The threat of climate change is clear and the change to renewables is an opportunity for the Upper Hunter to secure billions of investment dollars in clean green energy and the industries which will follow," Mr Shoebridge said.

Thursday's announcement from the Greens comes after Premier Gladys Berejiklian and Deputy Premier John Barilaro visited Singleton in support of Nationals candidate David Layzell on Wednesday.

The visit came on the same day that former Dungog mayor Tracy Norman announced her candidacy as an Independent.

The May 22 poll was scheduled after Nationals MP Michael Johnsen resigned last month following allegations of sexual assault - which Mr Johnsen denies.

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