London (CNN Business) Four former heads of the Federal Reserve have warned that an erosion of the central bank's independence will undermine financial markets and damage the economy.

In an apparent public rebuke of President Donald Trump , Paul Volcker, Alan Greenspan, Ben Bernanke and Janet Yellen wrote in an op-ed published by the Wall Street Journal that the US central bank must be able to make decisions "based on the best interests of the nation, not the interests of a small group of politicians."

"We are united in the conviction that the Fed and its chair must be permitted to act independently and in the best interests of the economy, free of short-term political pressures and, in particular, without the threat of removal or demotion of Fed leaders for political reasons," the former Fed chiefs wrote.

Trump named Powell, an investment banker, in late 2017 to succeed Yellen as chair of the Fed, the world's most powerful central bank. The Fed cut interest rates last week for the first time in 11 years, a move that some economists questioned because the US economy is relatively strong and unemployment is low.

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