The SIS x-clear system was due to go live on Friday but was delayed after LCH.Clearnet - which is currently the only clearing provider for LSE-listed stocks - reportedly imposed a charge to access business on the exchange.

A spokesman for SIS x-clear told Finextra that the clearing house is "technically and operationally ready" to launch the UK service and to switch over any new users.

But he claims that SIS x-clear is "suffering because of a lack of cooperation" from LCH.Clearnet.

The LSE inked a deal with SIS x-clear in 2006 that allows its customers to choose whether to clear trades through the Swiss central counterparty or via LCH.Clearnet - the sole clearing provider for the exchange's equity business. At the time SIS x-clear said it was determined to undercut fees charged by LCH.Clearnet.

A LSE spokeswoman told Finextra that the exchange is keen for the situation to be resolved and is working with both clearing houses "behind the scenes" to reach a solution.

LCH.Clearnet has so far declined to comment on the situation.

The London clearing house has supported the code of conduct but is reported to be blocking SIS x-clear in protest at barriers it is facing itself in Europe, particularly Germany and Italy.

Last year LCH.Clearnet issued formal requests to Deutsche Börse and Borsa Italiana for full interoperability with Eurex Clearing and Cassa di Compensazione e Garanzia respectively. The link ups would enable market participants to consolidate clearing of cash equities traded on four separate European markets - LSE, virt-x, Deutsche Börse and Borsa Italiana - at LCH.Clearnet.

But LCH.Clearnet seems to have hit a stumbling block as regulations in Germany and Italy are thought to require the London clearing house to set up a local bank in order gain access to local markets.

The code of conduct on clearing interoperability was agreed by securities markets participants under the threat of legislation from the EC, which was concerned about the high costs of share trading across European border.