Tasmanian winemakers are under pressure from mainland producers offloading cheap products on the island state.

An estimated 200,000 tonnes of Australian grapes are without a market and that has forced down prices along the supply chain.

Vineyards Association of Tasmania president, Stuart Bryce, said wholesale discounting had seen some mainland wines at half their normal retail price.

"The price differential between Tasmanian wines and mainland wines has opened up considerably, forcing consumers to rethink their purchases," he said.

"Tasmanian producers have little room to manoeuvre because economies of scale mean price reductions to maintain the differential are out of the question.

"Any reductions now will cause problems later when attempts would be made to ratchet prices back to where they belong."

Tasmanian growers produced about 6000 tonnes of grapes this year with Pinot Noir and Chardonnay the dominant varieties.