The Federal Reserve has kicked off one of the largest reductions of US bank capital requirements since the 2008 financial crisis by proposing to allow higher leverage at the biggest American banks.

The US central bank said on Wednesday it planned to slash the enhanced supplementary leverage ratio for the biggest banks. The rule requires them to have a preset amount of high-quality capital against their total leverage, which includes assets such as loans and off-balance sheet exposures such as derivatives. It was established in 2014 as part of sweeping reforms in the wake of the financial crisis.

Big banks have long been calling on regulators to ease the supplementary leverage ratio, complaining it punishes them for holding low-risk assets such as US Treasuries and hinders their ability to facilitate trading in the $29tn government debt market.