The administrator, based at the hospital and stood down yesterday, took responsibility for manipulating data for small improvements on waiting and treatment times for what is believed to have started as early as the end of 2010.

However, no explanation has been given into what motivated the staff member to change the data.

Health director-general Dr Peggy Brown faced media this morning  and said an external validation process identified an anomalous data pattern two weeks ago.

“We then progressed an internal investigation that uncovered the actual data manipulation and subsequence to that investigation an individual has acknowledged responsibility for altering the data,” Dr Brown said.

“The overall affect is a small change, we are yet to determine the full impact of the change because there are a lot of records we have to go back and correct.

“In relation to the national emergency access targets under the new National Health Reform, we believe there has been an overall change of approximately 2 per cent.”

The Opposition says the Government has “admitted to an unprecedented breach of trust, revealing that the community has been fed lies over hospital performance for at least the last two years”.

“The last time we saw an ‘independent’ investigation into the health system the government appointed their own investigator and covered up the findings. This government’s track record of vindicating itself must end,” Opposition Leader Zed Seselja said.

“Katy Gallagher has absolutely no credibility when it comes to being honest with Canberrans on the health system, and we won’t accept her own appointment of an investigator on this very serious issue.”

Opposition’s health spokesperson, Jeremy Hanson said Katy Gallagher’s dishonesty with Canberrans over the health system must end.

“Katy Gallagher was dishonest with Canberrans about elective surgery waiting times, dishonest with Canberrans about bullying in obstetrics at Canberra hospital, and now we see the dishonest manipulation of hospital data at the heart of her Department,” Mr Hanson said.

“It is blatantly clear that Katy Gallagher hasn’t been upfront with Canberrans about the health system and only a truly independent investigation will give Canberrans the full story which they deserve.”

Dr Brown said this was the first time she was aware of any suggestion of deliberate data manipulation or deliberate data changes.

“I don’t think it’s reasonable to speculate as to what may have been the reason behind the actions they have taken I will note however there was no personal or financial gain for the individual,” she said.

“I think they have made a very serious error of judgement and seeking to slightly enhance the performance data has been a very misguided decision.”

As well as the forensic audit of the ED data, expected to take several weeks, there will be an overall review of the data collection and reporting systems at the hospital.

Dr Brown said this was the first time that she was aware of any suggestion of deliberate data manipulation or deliberate data changes.

However, she said there was two incidences in the last couple of years where the Health Directorate has corrected data, including a minor change to operating theatre data and changes as a result of an Auditor General’s report into waiting lists for elective surgery and medical treatment.

Dr Brown said no further action will be made until the completion of the investigation.