It said its exposure to gas would grow to 0.91% of its loan book by 2030, before falling to 0.4% by mid-century, saying gas was a transition fuel as it emits less carbon than oil or coal.
CEO Sim Tshabalala said Africa needed to develop its economies, ensure reliable power supplies and cut poverty.
“A total or immediate ban on further transitional projects in Africa in order to help reduce environmental pressure in much richer regions would be a cost too far,” he said.
But campaigners say continuing to fund fossil fuels, including gas, will harm developing countries by driving climate change and make them more reliant on fossil fuels.
Standard Bank said it wanted to mobilise up to 300 bln rand ($19.9 bln) in sustainable finance — potentially including for transition fuels like gas — by the end of 2026 from a targeted 40 bln rand in 2022.
It set targets for reducing lending to coal, oil and gas as a percentage of its loan book by 2050, and its strategy put it ahead of some local peers.
But Standard Bank did not guarantee an absolute reduction in its financed emissions, unlike global peers such as HSBC and UBS, so lending in this area could grow if its loan portfolio expanded.
Maaike Beenes, an campaigner at BankTrack, which tracks bank finance activities, said the absence of near-term emissions targets and other caveats meant Standard Bank's policy fell short of even some local rivals.
“That makes it even more disappointing that Standard Bank seems to have missed the opportunity to become a climate front-runner with the policy announced today.”