The boss of embattled security firm G4S is facing mounting pressure to explain why he only learned "eight or nine days ago" that his company was struggling to find the 10,000 staff it was contracted to provide for the Olympic Games.
Speaking publicly for the first time since details of the fiasco emerged, Nick Buckles said he was "very sorry" 3,500 extra troops had to be drafted in at the last minute to make up the shortfall.
His apology came as it emerged that Home Office ministers were warned about security issues surrounding the Games 10 months ago.
HM Inspectorate of Constabulary (HMIC) raised their concerns in a confidential report in September 2011 following a number of inspections to test that the security plans of Locog - the Games organising committee - were on track.
But, contrary to reports, no investigations were made into G4S and the "issues" flagged by HMIC had all been dealt with by February of this year, the Home Office said.
The Government department added that it was only last Wednesday that it became clear that the security contractor was not going to meet its commitment and that thousands of additional troops would have to be drafted in.
Mr Buckles, who faces a grilling from MPs next week, insisted that both ministers and Locog had been kept fully informed of what was happening and said the company had been "fully transparent" about the difficulties it encountered.
G4S, the world's biggest private security company, is now looking at a loss of between £35 and £50 million following its failure to meet its contractual obligations.
Mr Buckles said there would be a penalty charge "in the range" of £10 to £20 million, although the bulk of the loss would come from having to reimburse the Government for the costs of providing the additional troops.