"It's only long enough if the process works properly, and it doesn't always."
Mr Davis said transparency was important.
Corrections said it has responded to the complainant and started an investigation.
Acting prison director Christine Faull told Fairfax that Corrections learned of the allegations on Wednesday.
"We encourage any prisoner with concerns to raise them with us so that they are investigated appropriately," Faull said.
"We demand a high standard of conduct and integrity from all employees, and as such, staff are expected to role model positive law-abiding behaviour."
She said the vast majority of staff "fulfil their duties with integrity and commitment in what is often a pressured and challenging environment."