European competition regulators are investigating whether a group of banks, including HSBC, Barclays and Deutsche Bank, are blocking the entry of new players into Europe's online payments market, the system used by consumers to buy products online.
The European Commission is examining the standardisation process for internet payments that is used by the European Payments Council, a body comprising 74 banks and banking associations. It is seeking to ensure that competition "is not unduly restricted", for example by excluding new entrants and payment providers.
A commission spokesman said: "Excluding competitors in the online payments market could result in higher prices for web merchants and ultimately consumers."
The EC said the investigation was prompted by a complaint from an unnamed party.
Joaquin Almunia, the EU Competition Commissioner, said: "Standards promote interoperability and competition, but we need to ensure that the standardisation process does not necessarily restrict opportunities for non-participants.
"Use of the internet is increasing rapidly, making the need for secure and efficient online payment solutions in the whole Single Euro Payments Area all the more pressing."
Mr Almunia is also investigating credit default swaps – essentially insurance on bonds – and the Libor bank lending rate. He has previously said the banks' collaboration on the payments system – known as Sepa – raises "complex challenges" for competition authorities.