The timescale of the North-South Inter-connector pylon project, running through Meath, Monaghan and Cavan, was cast into doubt last night.
The project was not included in the independent commission carrying out an investigation into the options of running underground.
And a planning application is expected on the North-South plan within the next three weeks.
If it is to be investigated, the planning application will have to be delayed.
Only the Grid Link, running from Cork to Kildare, and Grid West, running from Mayo to Roscommon, were handed to the commission.
But Fine Gael TDs claimed the North-South line was to be part of the investigation on running pylon lines underground.
Although there was no evidence this was the case, party backbenchers Sean Conlon, Ray Butler, Helen McEntee and Heather Humphreys met with Taoiseach Enda Kenny.
Mr Conlon said Mr Kenny had agreed to extend the remit of the commission.
The Taoiseach is believed to have told the backbenchers he will look into having the North-South line examined - but gave no guarantee.
EirGrid wants to run a 400 kilo-volt power line overground from Meath to Tyrone.
The commission chaired by former Supreme Court judge Catherine McGuinness will look at the underground options on the Grid Link and Grid West projects - not the North-South line.
A Government source said the North-South Interconnector was not included in the investigation.
Communications Minister Pat Rabbitte was solely responding to public consultation on "more recent and less well advanced projects", the source said.
EirGrid have already decided the route of the North-South line and the planning application will be lodged inside three weeks.
Mr Conlon claimed Mr Kenny had agreed to extend the remit of the expert commission to the North-South Interconnector.
He said it was a "game-changer" and the panel would be able to incorporate existing research and commission new work, if it was not satisfied.