Troops have been drafted in to help provide security at Olympic Games venues
Pressure is mounting on the chief executive of G4S after he apologised for failing to recruit enough security staff for the London Olympics.
Nick Buckles said the private contractor only became aware of the situation "eight or nine days ago".
He is due to appear before the Home Affairs Select Committee on Tuesday to answers MPs' questions, reports the BBC.
The Home Office said issues raised by inspectors about security last year were dealt with by February.
Buckles told the BBC that problems with G4S's recruitment and deployment of security staff for the Games had only recently been identified, after it emerged last Wednesday that 3,500 troops were being drafted in to plug the gaps in provision.
"I began to know it was going wrong eight or nine days ago. Basically we are recruiting a large number of people and they are all working through a process of interview, two or three different degrees of training, licensing and accreditation.
"It is only when you get closer to the Games, you realise that the number is not as high as you expect," Buckles added.
Buckles indicated in an interview with the Sunday Telegraph, he indicated that he "could quit" over the fiasco.
"I have got to make sure we deliver this contract. What happens thereafter is down to others. It's a big setback for us, we are really disappointed with how this has turned out.
"I want to stay. I have been here 27 years, I am very committed to staying. It just depends, doesn't it?"
Asked if he had considered resigning, Buckles said "of course".
G4S will lose between £30m-£50m on the contract, which is worth a total of about £280m.
The Commons Public Accounts Committee has summoned G4S, two government departments and Games organiser Locog to answer questions in September.
The Home Office said reports suggesting HM Inspectorate of Constabulary (HMIC) warned ministers over problems with G4S's ability to provide security for the Games were "inaccurate".
A Home Office spokesman said: "HMIC never undertook an investigation into G4S.
"We asked HMIC to carry out a number of inspections to test that Locog security planning was on track.
"While an early inspection highlighted issues to be addressed, a report in February 2012 said that Locog was on track to deliver the required number of security personnel."
The HMIC report went to ministers in September and was not made public. At the time G4S was contracted to hire 2,000 security guards for the Olympic Games. That was increased to 10,000 following a security review in December.
The Home Office said HMIC was critical of the plans but that later assessments were more positive.
Home Secretary Theresa May has said she was only made aware of the scale of the problem at G4S last Wednesday.