According to a Financial Times report, the European Commission's competition department will investigate whether the integrated settlement system - dubbed Target2-Securities (T2S) - violates EU antitrust rules or constitutes a "restrictive business practice".

Neelie Kroes, the EU competition commissioner, told reporters that the EC's financial services committee has been informed that the ECB is not exempt from competition rules.

Kroes added that the EC "would not necessarily find the system incompatible with EU competition rules" and could turn out to be "pro-competitive", but it will be examined carefully.

European Union finance ministers have already caused the ECB to delay a decision on whether the integrated settlement system should be introduced in the euro zone.

A decision was expected in March, but the ECB has agreed to calls to conduct further research into the scheme and provide more information on the costs and benefits of T2S.

The ECB has argued that an integrated securities settlement system - which would connect all clearing networks in the euro zone into a single platform and compete with private-sector settlement providers - would cut settlement costs by up to 90%.

But the plan has come under fire from the European Central Securities Depositories Association (ECSDA) - a trade association of 42 settlement bodies - which has called for the ECB to postpone the plans and conduct further study and consultation.

Earlier this week the European Credit Sector Association (ECSA) - which comprises of The European Banking Federation (EBF), The European Savings Banks Group (ESBG) and The European Association of Co-operative Banks (EACB) - came out in support of the system, but only if banks were given more control over the design and implementation of the system.

ECSA also called for banks to have direct access to T2S - which is at odds with the ECB's current plans which suggest that only national settlement companies would have access to the system.