Both lanes of the newly completed Belfast-Newry carriageway have had to be dug up after they began to subside, the Belfast Telegraph can reveal.

Fresh work to excavate and rebuild the lanes at a section north of Sheepbridge is expected to add around six weeks to the expected completion date for the A1 roads scheme, the Department for Regional Development has revealed.

The culprit is a stretch of boggy land where large amounts of peat had been removed — but some soft material remained, causing a stretch of the A1 road to “settle”.

DRD insisted the added work will not cost the public purse any additional funds.

A Roads Service spokesman said: “Monitoring of the new carriageway immediately north of Sheepbridge has identified a localised area of settlement.

“The location is one where very soft ground conditions existed and substantial volumes of peat were removed.

“Subsequent investigations indicate that small volumes of soft material still exist below the new carriageway and is the source of the problem.

“In order to remedy the situation the Construction Company commenced the necessary excavations on Monday April 19 2010 and the work is likely to take up to six weeks to complete.

“There is no additional cost to the public purse associated with these remedial works.

“The construction contractor and Roads Service appreciate the patience of the motoring public during the works and would ask that particular care and attention be exercised during this specific period.

“Roads Service can confirm that the A1 Beech Hill to Cloghogue dualling scheme remains several months ahead of schedule and is expected to be made available to traffic during summer 2010.”

The scheme is designed to dual the final sections of the A1 that were not already dual carriageway.