Local contractors allege that the failure of a landscaping company undertaking work at the Campbell site is being used as an excuse for delays to the $633 million project which is $175 million over budget and more than 18 months behind schedule.

But the federal government department responsible for the project says it has allowed fair access to the documentation the builders needed to pursue their case.

Canberra landscaping company Urban Contractors, which collapsed in October 2012, is in dispute with the main contractor at the giant site, Bovis Lend Lease, and is trying to recover millions of dollars it owes to other businesses around the capital.

Two adjudication decisions, under the Security of Payments Act, have gone against Urban and some of the contractors are blaming in part the secrecy surrounding ASIO.

All contractors on the site have had to sign secrecy agreements. But one businessman involved in the job and owed money told The Canberra Times that contractors felt a sense ''of injustice'' at their treatment by Lend Lease.

''There are a lot of unresolved items there, about $20 million work has been done and about $14 million has been paid,'' he said.

The contractor, who asked not to be named, said the secrecy provisions had seriously hampered Urban in the adjudication process.

''The adjudication has to be given on the documents that were given and the documents were inadequate and there wasn't enough time, within the law, to get the documentation out,'' the builder said. ''It was restricted and what was released was only partly released.

''The process of getting it available was to get a couple of lawyers security cleared and for them sit down at a computer terminal on the site watched by an ASIO guy or two and go through the documents requesting which ones they wanted.

''That's OK if you've got all the time in the world to prepare a legal case, but if you've got a limited time, under the adjudication legislation we only had 10 days.''

The contractor said Urban Contractors' administration was being used as an excuse for more delays in the occupancy of the building, originally scheduled for March 2012, but now delayed until August 2013.

''All their Christmases came at once when Urban went down because then they had an excuse, but the reality is that building is still not ready,'' the man said.

Urban Contractors principal Mick Burgess declined to comment and Administrator John Morgan of BCR Advisory said the adjudications were confidential.

Bovis Lend Lease referred inquiries to the Department of Finance and Deregulation where a spokesperson denied there had been any restrictions on access to documentation. ''The time-frames imposed were stipulated by the adjudication process between Lend Lease and Urban Contractors,'' the department said.

''This process was initiated by Urban Contractors.

''The Commonwealth facilitated access to documentation and did not deny any request for documentation by Urban Contractors.'' The department said insolvencies among contractors was to blame for the latest delays.