Nick Buckles said G4S hasn't lost any customers from the Olympics but the firm has to "rebuild the reputation".
Nick Buckles said he can't talk about why G4S messed up the Olympics contract because there is an ongoing review of what happened which isn't finished yet.
But he says the initial requirement of 2,000 staff was increased to have 15,000 staff on standby. He said they realised they had problems in early-July.
He emphasises that 7,000 military were always expected to work alongside G4S but additional troops were drafted in to help them with the shortfall.
He is spending quite some time saying how complex the Olympics contract was - maybe so, but they signed up to it.
G4S are still in talks with Bedfordshire, Cambridgeshire and Hertfordshire Police over providing services. Nick Buckles, chief executive, says the Lincolnshire contract is going well.
It's extraordinary to hear Buckles rattling off a list of public deals - Oakwood Prison, other jails, Scottish courts, police contracts.
Whether it's a good or bad idea to involve the company, this morning is a big reminder of just how much business G4S does with the Government.
G4S admit that the Olympic security fiasco cost them £50 million but their profit was more or less the same as the same period last year, at over £230 million.
There has been a sharp drop in G4S net profits though - £38 million versus £118 million for the first six months in 2012.
The firm has promised no problems at the Paralympic Games though.
Nick Buckles, chief executive of G4S, said the security firm will "continue to play a major role in this sector" despite the failure to deliver its Olympic contract.
G4S is conducting an internal review after its failure to provide all of the 10,400 contracted guards for London 2012 forced the Government to step in with military personnel.
The overall business has performed well in achieving a similar underlying profit as the first half of last year despite economic challenges, particularly in Europe, and weakness in the US government market.
Underlying organic growth in the first half has improved to over 5% overall driven by a strong performance in developing markets which grew by over 10%.
We continue to see good opportunities from outsourcing around the world particularly from governments looking to improve quality of services and reduce costs and we believe that, with our long-term track record, we will continue to play a major role in this sector.
The breadth of our portfolio in 125 countries continues to present many new growth opportunities. Our market leading businesses, broad customer base and £3.8bn per annum contract pipeline give us confidence in the outlook for the Group.
The security firm G4S has said it had delivered 83% of contracted shifts for the Olympics and that it was confident the Paralympic Games would be fully staffed.
The chief executive of G4S Nick Buckles said he was "deeply disappointed" with the security firm's failure to fulfil its Olympics contract, according to Sky News.
We are deeply disappointed that we had significant issues with the London 2012 Olympics contract and are very grateful to the military and the police for their support in helping us to deliver a safe and secure games.
The Sun's Business Editor Steve Hawkes has tweeted that only a small number of the G4S job cuts will effect the UK.
G4S insists only a handful of 1,100 job cuts in UK and most have already happened