The European Union has asked national bank regulators in the 27-nation bloc to explain policies that may be preventing free flows of funds across national borders, the first public step in a campaign by EU authorities to combat fragmentation of the region's financial markets.

The free movement of money is a central pillar of the EU's single market, but some actions by national authorities since the onset of the financial crisis in 2008, intended to protect local banking systems, have prevented banks from moving funds to other countries.