Bernard Brennan said he was recently accepted to work as a team leader at the City of Coventry stadium during the Olympic Games.
He said he was then told several days later he would no longer be needed but has since seen similar jobs advertised.
A spokesman for G4S said: “We are sorry that potential employees have experienced difficulties.”
Mr Brennan, previously a security adviser at University Hospitals NHS Trust Coventry and Warwickshire, said G4S had confirmed a week ago he had a role as a team leader.
He said he was then told on Thursday that he would no longer be needed, but found an advert for a security job with G4S on Friday at the stadium through a local employment agency.
‘Excuse after excuse’
Mr Brennan said: “I’m very frustrated, I’ve been unemployed since November and my background has been in security.
“For me this job wasn’t just a job, I take pride in what I do and I was excited to have an opportunity to get involved in the Olympics but to be told ‘thanks but no thanks’ is very annoying.
“It’s been excuse after excuse after excuse in this jobs fiasco – they got my accreditation through but said they didn’t think they’d get my references through in time for the Olympics.”
Earlier this month G4S admitted it would not be able to supply all of the 10,000 security staff to Locog and 3,500 UK armed forces personnel are to be deployed to make up the shortfall.
A statement from G4S said: “While we aren’t able to comment on individual cases, we are sorry that potential employees have experienced difficulties through the recruitment process.
“The large increase in numbers of staff requested by [Olympics Games organiser] Locog has been extremely challenging, and we have encountered some delays in progressing applicants through the final stages.”
Mr Brennan said: “I don’t think they’ve dealt with it very well and my view is that G4S have just tried to put bums on seats and have lowered the standards in relation to how they’re recruiting.”