The Bank of England’s powers to tackle climate change risks in the financial system could be given an overhaul to reflect the scale of the “emergency” facing the planet, John McDonnell has said.

Speaking after Mark Carney, the Bank’s governor, used an article in the Guardian to warn financial firms that they faced an existential risk from global warming, the shadow chancellor said Labour was exploring ways to retool Threadneedle Street.

Welcoming Carney’s intervention in a tweet on Wednesday, McDonnell appeared to suggest that more action was required to meet the challenges of climate change.

John McDonnell MP (@johnmcdonnellMP) Mark Carney's intervention is breakthrough moment. In addition to rewriting government spending criteria we’ll now consult on changing the Bank of England's mandate to reflect the climate change emergency highlighted by #ExtinctionRebellion Rebellion demo. https://t.co/n7M7qBnp8j

McDonnell has been examining various ways to reshape the Bank’s mandate, which is set by the government, should Labour come to power.

He has previously focused on giving Threadneedle Street greater powers to direct the lending of commercial banks into more productive sectors of the economy, and away from property speculation. Labour is also considering ways to funnel more investment into green industries and technologies, which will encompass how the role of government and other agencies, such as the Bank, can be used to tackle climate change.

The party has already said it would rewrite the Treasury’s green book, the manual for government spending decisions, and that the Office for Budget Responsibility, the tax and spending watchdog, would be mandated to consider climate risks in its economic forecasts.

The Bank said on Wednesday it would disclose an assessment of how it managed climate-related financial risks as part of its 2019-20 annual report, a regular update on its work, which will come out next year.

Carney said the central bank would adopt the framework of the taskforce for climate-related financial disclosures (TCFD) – a G20 initiative calling on commercial banks to disclose their lending to companies with carbon-related risks – to publish details of its own risks from climate change.

“We need to lead by example and by providing such disclosures, we will be playing our part to secure the transition to sustainable financial system,” he said.

Campaigners have argued that the Bank could do more to tackle risks from climate change, including forcing the mandatory disclosure of carbon-related assets, rather than asking banks to consider doing so.

Threadneedle Street could also force banks to set aside more money to protect from losses on carbon assets, or encourage them to lend to green projects by reducing the amount of money they are required to set aside.

Rob Macquarie, an economist at the lobby group Positive Money, said: “Central banks have a crucial role to play in decarbonising the financial system, but continually present their mandates as a restriction against adopting certain climate-friendly policies. We therefore welcome moves from the Labour party.”