The Bank of England, the central bank of the United Kingdom, needs to increase its capital to assuage systemic risk, John Vickers, chairman of the Independent Commission on Banking, warned in a Financial Times op-ed Sunday. Vickers and his team made suggestions for greater insurance measures in 2015 that the BoE did not heed, exposing it to continued risk, he said.

Given the awfulness of systemic bank failures, ample insurance is need­ed, and equity is the best form of insurance,” Vickers wrote, adding, “The recent volatility in bank stocks underlines the importance of strong capital buffers. The BoE should think again.” 

The controversy centers on how much capital a bank needs to protect itself from shocks to the market. Vickers, a former BoE chief economist, said the bank needed more capital than it currently has, particularly high-quality capital in the form of shares.

Stock markets throughout the world have seen great volatility in the second half of 2015 and into the new year following a Chinese economic slowdown in August. An oil glut caused by the shale boon, overproduction in the Middle East and reduced demand for oil in emerging markets have sent the price per barrel of crude oil plummeting in the past several months, reaching 12-year lows of less than $27 per barrel. A commodities rout has caused significant losses for investors, and European bank stocks in particular have suffered, losing 25 percent of their value since the beginning of the year, the BBC reported.

“A good way to think about it is as an insurance policy,” Vickers told the BBC, adding, “You do have to pay a premium to insure your house, and you hope nothing bad will happen. But if it does, you are much better off in paying that premium, and for full coverage.”

The U.K. also faces its own economic uncertainty as a referendum on an exit from the European Union looms in 2016. Economists have warned the U.K.’s economy would take an immediate hit if it were to leave the EU, and speculation concerning a so-called Brexit has contributed to market volatility, according to International Monetary Fund leader Christine Lagarde.