In a new policy statement released on Friday, Westpac said it will only lend to to new coal mines with an energy content of at least 6,300 kilocalories per kilogram.
Given that the coal from the Adani Carmichael project in the Galilee Basin is relatively 'dirty' and well below 6,300 kilocalories per kilogram, Westpac's statement effectively rules out funding the project.
The announcement comes after an anti-Adani activists disrupted Westpac's 200th birthday celebration dinner on 8 April.
The bank has also committed to lending $10 billion to climate change solutions by 2020 and $25 billion by 2030.
Westpac chief executive Brian Hartzer said, "Westpac recognises that climate change is an economic issue as well as an environmental issue, and banks have an important role to play in assisting the Australian economy to transition to a net zero emissions economy".
Westpac joins 17 other banks around the world that have indicated they will not fund the Adani project, including Standard Chartered, BNP Paribas and Credit Agricole.
As for the big Australian banks, NAB said in September 2015, "NAB is not involved and has no plans to be involved in any financing for the Carmichael coal mine."
The Commonwealth Bank ended its relationship with Adani as financial advisers in August 2015, but has yet to rule out future loans to the project.
ANZ chief executive Shayne Elliott has said his bank's exposure to coalmining is "pretty small and trending down and I can't see a time where we'd suddenly see that trend shift, to be honest".
Environmental finance campaigner Market Forces said Westpac's announcement also amounts to a "de facto exclusion" on new coal power stations.
"With this policy change, Westpac has raised the bar on climate change for the other big banks, becoming the first major bank to put restrictions in for new thermal coal mines”, said Market Forces executive director Julien Vincent.
"The fact that an existing lender to Adani has now ruled out financing the proposed Carmichael mine makes this announcement even more significant."
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