The interconnector, which links the power grids of Ireland and England, has been causing serious disruption to phone lines along its route from Batterstown, Co Meath, through north County Dublin and across the Irish sea to Wales.
Fianna Fáil Finance spokesman Michael McGrath said the situation was embarrassing for the Government.
A spokesperson for Eirgrid said once it became aware of the technical issues, it deferred commercially operating the interconnector.
“EirGrid had aimed to commence commercial operation of the interconnector in early October following the completion of satisfactory testing. This would have seen the Interconnector delivered three months ahead of schedule.
“However, following reports of possible telephone noise interference in the vicinity of parts of the land route, further testing was required and the commercial operation was temporarily deferred.”
Eirgrid has refused to take over the interconnector from the contractor ABB until the issues affecting the telephone lines have been resolved.
Eircom found complaints from customers about noise on the line were clustered in the vicinity of the interconnector power ducts and were coinciding with the tests being run by Eirgrid.
An interim solutions has been adopted by Eircom where it applied filters to certain phones, but it is understood that ABB will have to provide a permanent solution to the problem requiring significant engineering works on the interconnector.
It is understood Eircom expects to be compensated for the work it has carried out.
To date the Interconnector has cost €570m. The funding has come from a €110m grant from the EU, a €300m loan from the European Investment Bank, €60m from EirGrid and a commercial loan from Barclays/BNP Paribas.
Eirgrid is eager to run the interconnector on a commercial basis and began running trials at a reduced capacity, which has demonstrated considerable reduction in the telephone noise interference.
“Therefore, this has enabled EirGrid to move into an extended trial mode from Dec 1 in full co-operation with the telecommunications network operator,” a spokesperson for Eirgrid said.