Federal Labor MP Michael Danby has refused to explain how and why he used Commonwealth limousines on personal holidays to Queensland that he later claimed were charged to taxpayers because of administrative error.

The Melbourne Ports MP charged taxpayers about $500 for COMCARs to and from the airport on three trips to the Gold Coast or Cairns for which he had no official parliamentary business. The trips took place in 2010, 2012 and 2015.

Michael Danby says the trips were charged to the taxpayer in error by his staff. Credit:Andrew Meares

Mr Danby says he reimbursed the Commonwealth for those holidays last year after a self-audit, including flights and car costs. He claimed the trips were charged to the taxpayer in error by his staff, caused by the fact he used the same booking agent for personal and business travel.

However, the COMCAR booking system is completely separate to the booking agency used for airfares. Mr Danby has also refused to explain how he could have taken a Commonwealth limousine to the airport for a personal holiday and failed to realise a mistake had been made.