Recent research by the Unclaimed Assets Register estimated that £15.3 billion lies unclaimed in accounts, pensions and shares.
Mr Clarke said: "Generally what will happen is, accounts which have been used for a specific reason say, saving for a holiday or something like that and are pass-book based, the pass-book goes in the bottom of a drawer and people tend to genuinely forget about them.
"In other cases, people move house and don't update their bank with a change of name and address; they don't get statements; and the account gets forgotten about that way."
Halifax provides a number of services to customers across the globe, including insurance and investment products.
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