Concerns have been raised over inconsistencies between driving test examiners around the country.

The public spending watchdog found some testers consistently passed or failed significantly more candidates than other examiners operating in the same centres.

The Comptroller and Auditor General also recorded a 13% difference in pass rates between Road Safety Authority (RSA) examiners and those outsourced to contractors in 2008.

RSA chief Noel Brett defended the organisation, saying its 121 testers underwent regular retraining and competence assessments.

He also said the contractors, Swedish firm SGS, were given a different type of candidate as officials attempted to reduce an average 69-week waiting list.

"Outside providers were given the people who were waiting the longest and who had not failed a previous test," said Mr Brett.

"We were testing people who were waiting the shortest time and who had failed in the past.

"The outsource contract ended in April 2009 once the back log was addressed."

The RSA took over the running of driving tests from the Department of Transport in 2006.

Mr Brett said tests were outsourced in 2007 and 2008 to clear the backlog of learner drivers on the road.