The Home Office is carrying out the immigration, criminal record and security checks on behalf of Olympic organising body Locog to help ensure the safety and the security of the Games.
Anyone who will take part in the Games – as an event worker, official or athlete – is being checked, in a process which began in October 2011.
After the checks, the Home Office will recommend to Locog which applicants should be refused or accepted.
Around 100 people have been rejected so far. A Home Office spokesperson told Event accreditation would be refused "to any individual it believes may present a safety or security risk or presence at the Games (or in the UK) may not be conducive to the public good."
The spokesperson added: "We are undertaking stringent checks on all those seeking accreditation. This rigorous process has been designed to ensure those working at the Games are fit to do so. We will leave nothing to chance in our aim to deliver a safe and secure Games that London, the UK and the whole world will enjoy."
This process has been designed in partnership with Locog, the International Olympic Committee and the International Paralympic Committee.
Security firm G4S is providing security staff for the Games and carries out its own security checks before the Home Office accreditation process.
A G4S spokesperson said: "G4S screen and vet all 2012 staff, the purpose of which is to check for criminal records and, among other things, candidates' credit and employment history. They are then further vetted by Locog under Home Office supervision. The details of that check, nor the reasons why some candidates are rejected, are not known to G4S."
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