At a Tuesday morning conference session devoted to T2S at the Swift conference in Boston, the two CSDs also questioned the projected savings forecast by the ECB and raised concern over its experience in running a major technology platform and the proposed governance structure of T2S.

The project, an extension of the Target2 payments platform, has been prompted by what the ECB sees as prohibitively high securities settlement costs in Europe compared to the US market. The central bank has outlined controverial proposals for an upgraded Target2 payments system to operate as a central hub for securities settlement in the Eurozone.

At the Sibos session, Euroclear and Clearstream stressed their support for the concept of a harmonised structure, but demanded far more clarity from the ECB about its plans for the system before committing to the project

"We are neither for nor against T2S. It is till to early to decide whether we will join a system that won't go live until 2013 and is voluntary," says Paul Symons, head of public affairs at Euroclear.

"We are being asked to outsource our settlement function to an organisation we don't know enough about. What is the legal structure? Is this a public sector organisation? How much influence we will have once it goes live?"

Symons was also sceptical of the ECB's "highly public reference" to a forecast cost of 29 cent for every security settled through T2S. Euroclear's current costs involve the provision of other services, such as reconciliation, custody and collateral management, says Symons. "Until we know what the end-to-end costs to our clients of T2S will be, we cannot say if we are in favour or not.

Symons views were supported by Katja Rosenkranz, head of section business strategy at Clearstream who was wary of the governance structure involved with T2S. "We are concerned about the role of the ECB. It wants to position itself as an IT provider but also has a regulatory role. We don't like to see these two roles combined. And we believe it should be the European Commission that should oversee competition issues between CSDs, not the ECB."