Australia's leading tea brand Lipton Quality Black have grown at a rate faster than the market since its maker Unilever decided to procure tea from sustainable plantations.

However, even with the $3 million sales fillip, both Unilever and the Rainforest Alliance, an environmental organisation that certifies the plantations, are not sure how much going green affects sales.

According to Unilever's marketing chief David McNeil, consumers in Australia put quality and value for money first. Using the line "Pick your tea with care," marketing underlined the ethical and environmental benefits of choosing tea from sustainable plantations as wells as sent the message that the tea brand had not compromised on quality.

Since the marketing campaign began a year ago, Lipton, which has a 26 per cent share of the $290 million Australian tea market, expanded by 4.2 per cent or more than twice the market rate.

Mr McNeil, who thinks happier workers, better conditions on plantations and a "superior end result" are strongly correlated, said consumers are interested in the story of their tea but it really boils down to quality and value for money.

Mr McNeil was convinced Lipton, which guarantees at least half the tea in every bag will be from sustainable plantations, became more popular largely because of its ethical credentials.

"Ever since we made it the core of our messaging, we've seen Lipton become more popular than other brands at a time when people have been more choosy and selective about how they part with their money."

Mr McNeil, however, cannot say how much "doing good" affects sales.

Rainforest Alliance likewise did not have any data on what made consumers purchase.

"I think this market is very motivated to buy sustainable but we don't have any studies or data that speaks specifically to that ... But we have seen growth in companies that work with us," said the organisation's co-ordinator Petra Tanos.

Meanwhile, Unilever announced it was on track to procure all its tea from Rainforest Alliance-certified farms by 2015.