As Germany's cabinet adopts plans for a bank levy today, finance officials fear German banks will face a double charge, one at home and the second in the UK, where similar plans are being cooked up.
The next meeting of EU finance ministers in Brussels, scheduled for 6-7 September, will likely try to resolve the issue, say EU diplomats.
This glitch will be discussed within an EU framework, a diplomat told EurActiv.
Germany's deputy finance minister, Jörg Asmussen, reportedly dispatched a letter to his counterparts in the UK Treasury, which warned that German banks could be doubly hit by both countries' plans for a bank levy, according to the Financial Times.
An EU diplomat said Asmussen's letter was merely intended for "informative purposes for countries that have more advanced plans for a bank levy".
Today, the German cabinet is expected to back a bank restructuring bill including a levy on bank assets estimated to raise around one billion euros annually to fund future bailouts, according to a government source.
The bill, which would come into force next year, would also allow the government to take a leading role in restructuring banks in dire straits.
Plans for a bank levy have been underway in Britain and Germany since G20 talks unsuccessfully tried to forge a multilateral agreement on charging banks a fee to pay for their own rescues.
In the EU, Internal Market Commissioner Michel Barnier has also endorsed an EU-wide levy which would feed into a dedicated fund to rescue defaulting banks.
This, and other proposals for a tax on financial transactions (FTT), will be discussed at the ministers' September talks.