Central banks are ready to intervene if Britain votes to leave the European Union (EU) at a referendum next week, ECB Governing Council member Ignazio Visco was quoted as saying today.

The prospect of the closely-contested vote, which will help determine Britain's future in trade and world affairs and also shape the EU, has rattled markets around the world.

"A British vote in favour of leaving the European Union is the risk that worries us the most at the moment," Ignazio Visco said in an interview with newspapers including Italian daily La Repubblica.

"We are keeping an eye on this risk day by day and all central banks, not just the European Central Bank, are ready to intervene with the conventional instruments they have: interest rates, repos, swaps," said Visco, who is also Bank of Italy governor.

Officials told Reuters last week the ECB would pledge to backstop markets in tandem with the Bank of England if Britons vote to leave.

Visco said the long negotiation process after an eventual "Brexit" vote would certainly have financial consequences but it was difficult to predict how serious they would be.

Campaigning for the referendum has been suspended after a British lawmaker was murdered in her electoral district in northern England on Thursday.