An insider at the project, which was designed by Foster and Partners, said the 19-storey building was a challenging job with testing technical details. He added that Skanska had so far only built up to the 10th storey, and that if it continued at this pace it would be severely late.
Skanska acknowledged that it had experienced groundwork problems on the scheme and said it was working with the client to mitigate them.
Hammerson, Greycoat and Henderson, the joint developers of the scheme, declined to comment.
The delay to Moor House coincides with trouble at another Skanska scheme in London, British Land's Abbey National headquarters at Triton Square, near Euston Station.
There had been speculation that the contractor was about to receive a writ for £10m from British Land, the project's developer.
Skanska was more than a year late on the seven-storey, £65m building as a result of problems with its M&E systems. The project is now complete.
John Weston Smith, British Land's financial director, said his firm was in discussion with Skanska, but refused to comment on details of any legal action.
One project insider said it was widely recognised that the project has been a disaster in terms of the time taken to complete it.
The insider said that British Land and Skanska were discussing a settlement.
Last year, the tenant on the project, Abbey National, threatened to pull out when Skanska missed a completion target of 6 April last year. British Land then agreed a six-week extension, which the contractor missed.
Skanska denied that a writ was pending, and said it had made a provision for a loss two years ago.