Virgin connected around 567,000 premises in 2015-16, not 715,000 as stated, the company said in a filing to US securities regulator the SEC, amending its 2016 annual report.
Liberty Global also revised its guidance for 2017 and now expects to connect 1.3-1.4 million premise and not 1.4 million as previously stated.
The 2017 guidance had included an estimate of 800,000 new addresses covered by Project Lightning but following a review, Virgin discovered in late February 2017 that completion status for inactive premises had been "misrepresented".
Overall, 142,000 addresses the company had reported as completed at 31 December 2016 were found to require further work.
It said four employees have been suspended as a result of the discoveries and may face disciplinary action, including dismissal.
While it expects all of the premises in question to be connected by 30 June, this will not affect the revised guidance.
The company said it has appointed a new management team to Project Lightning as well as a new managing director who will report to Liberty Global’s chief technology officer and the CEO of Virgin Media.
Virgin Media has also appointed a new chief operating officer responsible for Project Lightning and Liberty Global said it will have additional resources to manage increased volumes of construction and planning activity in the UK.
The company also revised its methods for reporting connected premises but said the revisions reported to the SEC have no material impact on its financial statements.
