Mr Fitzgibbon said the smoke taint that has forced several wineries to cancel vintages in the Hunter and areas including Cowra and Mudgee.

"Wine is a $40 billion industry in this country," Mr Fitzgibbon said.

Mr Fitzgibbon's call for clarification arrives as a second major Hunter Valley wine producer, McWilliam's Mount Pleasant, has joined Tyrrell's Wines in writing off the 2020 vintage.

In an email issued to his wine club members, Mount Pleasant chief winemaker-manager Adrian Sparks said it had been decided not to pick any grapes for Vintage 2020.

He said the decision was made after laboratory and sensory analysis of the estate, Rosehill and Lovedale vineyards and third-party testing.

"This painstaking choice was not made lightly," said Mr Sparks. "We have nearly a century of history at Mount Pleasant and vines almost 140 years old, and with this comes the responsibility to ensure that we uphold the highest integrity when making wine for you. We will not compromise on quality or take any unnecessary risks when it comes to this."

Mr Sparks said grape tests have been carried out across the whole of the Hunter and he was unsure how other producers have been affected.

"There are likely scenarios where there are clean grapes in other pockets of the region," he said. "We are therefore hopeful that other vineyards have been more fortunate and have not seen the levels of smoke exposure our vineyards have."

Tyrrell's decided last week that most of its vineyards would not be harvested for wine production and it would have a severely reduced 2020 vintage.

Mr Sparks said many parts of Australia had been gripped by the worst bushfires in living memory, with people losing their homes, their livelihoods and worse still, the loss of life. Constant exposure to smoke could result in vines absorbing taint compounds in the sugar molecules, giving grapes and the wines produced burnt, smoky, medicinal or "dirty ash tray" characters.

Mount Pleasant had sent many samples off for testing with Australian Wine Research Institute (AWRI) and Vintessential Laboratories.

With the help of LaTrobe University, it had also installed measurement devices in the prized Lovedale vineyard and had been conducting micro-ferments in the Pokolbin winery laboratory to detect taint in the fruit before picking.

- with MATT CARR

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