UK banks will be required to build a buffer of loss-absorbing bonds at least as big as the capital already held under new international rules, according to a Bank of England (BoE) official.The crackdown comes as part of plans to prevent governments having to bail out banks in the event of a financial crisis such as in 2007-2008. BoE's Executive Director of Resolution Andrew Gracie said the buffer must be sufficient to restore the bank's basic capital requirement, Reuters reported. Banks have to hold capital equivalent to 7% of their risk-weighted assets under new world rules.An even larger amount of bonds might be needed at the largest banks, such as Barclays and HSBC, to ensure the restructured lender is sustainable, Gracie said."For a bank that has undergone resolution to command market confidence, it is likely to need at least as much capital as other banks in the market," he added.Many of the major banks now have a basic capital buffer of about 10% or more as an extra precaution. RD