Refurbishment of the prime minister's official Canberra residence will cost taxpayers more than $8.8 million - at least $5 million more than originally expected.
Work on The Lodge is expected to be finished in July and will cost $8.842 million, dwarfing the original $3.19 million price tag.
Originally expected to take 18 months and be completed by mid-2014, Finance Department officials have pushed back the completion date at least three times as the scope of works has been expanded.
Work on the historic Deakin home originally included asbestos removal, replacement of the slate roof, heating and cooling system upgrades, new lights and electrical wiring, painting, a new kitchen, bathroom improvements and health and safety upgrades.
Finance officials told Senate estimates last month the scope of works, overseen by head contractor Manteena, had been expanded to include security systems, "functionality and liveability" improvements to living areas and bathrooms and work on rundown external guard houses adjacent to the property's walls.
After contractors finish on site, heritage furniture, curtains and artworks owned by the Australiana Fund will be returned to the 40-room interior.
On Monday, a spokeswoman for the Department of Prime Minister and Cabinet denied the cost of the works represented a blow out of the project's budget.
"Preparations are progressing for the move back into The Lodge but a specific date is yet to be identified as it is contingent on completion of exterior works," the spokeswoman said.
"Once the interior works have been completed, the installation of soft furnishings, furniture, equipment and artworks is expected to take up to four weeks. The Lodge will be ready for occupation on completion of the external works."
A fine art adviser from the Australiana Fund will supervise movement of historic items but is yet to be told when the move will take place.
Originally commissioned under the former Labor government, costs have grown steadily. In April 2014, the cost was calculated at $4.45 million. By December, the contract was varied to $6.38 million. The Abbott government's first budget included unspecified extra funds for the work.
Prime Minister Tony Abbott has previously said he would lean towards "orthodoxy" and live in the home. Designed by Melbourne architects Oakley and Parkes, prime minister Stanley Melbourne Bruce and his wife Ethel Bruce first moved into the colonial revival-style home in May, 1927.
Originally known as the Prime Minister's Cottage, the heritage-listed home cost more than £28,000 to build.
The government has sought to avoid information about the refurbishment being made public.
Staff in Mr Abbott's office declined media requests for information fearing "negative comments" about the project.
Internal documents released under freedom of information laws showed bureaucrats were instructed to give purposefully vague responses to requests for information from The Canberra Times.
Emails showed officials were told not to provide any explanation or identify Mr Abbott's office or the Department of Prime Minister and Cabinet as being responsible for blocking information being released.
One senior bureaucrat said Mr Abbott's staff could be concerned about privacy or a poor reaction to the information being made public.
In March, officials said they had created 980 pages of documents explaining why refurbishment works were behind schedule. Responding to a freedom of information request, Finance sought $67,825 to release the documents.
A revised request from a 12 month period attracted a $3759 price tag. Nearly 14 hours would be needed to retrieve documents and it would take 176 hours for bureaucrats to decide what could be released.
Prime ministers including John Howard, Ben Chifley and James Scullin all famously snubbed The Lodge, while 15 former leaders including Kevin Rudd and Julia Gillard used the residence during their tenures.
Mr Abbott has opted to stay in a $110-a-night room at Australian Federal Police College in Barton.
Taxpayers were charged $65,000 in lease-termination fees after Mr Abbott chose not to use a $3000-a-week home in Forrest rented during the pre-election caretaker period.
Last year the Attorney-General's Department launched a review of perimeter security controls after an elderly driver crashed his car through the protective brick wall.