A G4S spokeswoman said:
This has been an unprecedented and very complex security recruitment, training and deployment exercise which has been carried out to a tight timescale.
We have encountered some issues in relation to workforce supply and scheduling over the last couple of weeks, but are resolving these every day and remain committed to providing a security workforce for the start of the London 2012 Games.
She went on:
Our planning with Locog and other security agencies allows for a variety of contingencies which have been reviewed in the build-up to the Games.
We accept that the Government has decided to overlay additional resources.
We remain committed to keep London 2012 safe and secure.
Faced with a list of last minute problems, ministers and organisers insist the Olympic security situation is under control.
Theresa May was tonight accused of giving MPs a "selective account" about when she knew G4S were having problems supplying Olympic staff.
MOD confirm picture of UK Olympics troops sleeping on chairs as they cover the G4S shortfall in Olympic security is genuine