The Australian Customs Service confirms that there have been more than 700 complaints made by employees about potential corruption within the department over a three-year period.
There were 724 internal complaints, allegations and concerns reported to Customs that related to the service's staff between 2007 and 2010, the BBC reports.
Customs has released a statement saying there was no proof of criminal conduct in 500 of those cases.
The statement goes on to explain it is impossible to work out whether the staff involved were internally disciplined in 300 of the matters, because there has since been changes to record-keeping systems.
Customs says in 39 of the cases, officers were found to have breached the Australian Public Service's Code of Conduct and were subject to "administrative action", including the loss of salary.
Customs chief executive Michael Pezzullo says the service has seen major improvements in its defences against corruption and misconduct since 2010.
In 2011, Customs came under the jurisdiction of the Australian Commission for Law Enforcement Integrity, which now handles all allegations of corruption and misconduct for the service and has the power to order investigations
"There is no place in the service for corruption, serious misconduct or fraud," he said in a statement.
Police arrested five people, including two Customs officers in February as part of a two-year investigation into corruption.
