HSBC, Europe's leading banker to corporate Asia, laid out its long-awaited policy on financing thermal coal on Tuesday, and said it expected all its clients to have a plan in place to exit fossil fuel by the end of 2023.

Coal is contentious for governments across Asia as they look to move away from the cheap and widely used (but carbon-intensive) energy source to help meet a global commitment to cut emissions in the fight against climate change.

Under its plan, HSBC will cut exposure to thermal coal financing by at least 25% by 2025 and then by 50% by 2030, although non-EU or non-OECD-based clients could be funded until a global phase-out by 2040, the bank's sustainability chief said.