The detail and even the merit of the Australian government's guarantee on bank deposits is testing financial regulators and the Cabinet.The Treasurer, Wayne Swan, confirmed in parliament yesterday that depositors may have to pay a fee to benefit from the guarantee on deposits of "more than $1 million" though the cap, if any, appears fluid.The Australian today reported that the Reserve Bank of Australia was pushing for a fee and quoted from a letter from Glenn Stevens, the RBA governor, to Ken Henry, the Treasury secretary.Stevens wrote that a guarantee cap at a level of $5 million, as was being discussed late last week, was incredibly generous by the standards of other countries. Stevens warned Treasury the sudden surge in demand for guaranteed instruments was creating "serious dislocation in the financial system".Stevens also wrote, according to the newspaper, that "not only must there be a cap, but the lower the better".