Australian architects want plans to erect 2.6-metre fencing around Parliament House put on hold while an urgent review is undertaken.
The Australian Institute of Architects has "deep concerns" about the level of public involvement in the decision-making about changes to the significant public building.
Parliament's presiding officers are refusing to consult the public over the new security fence - citing national security concerns - despite growing demands by MPs for the plans to be published before works commence.
Institute president Professor Ken Maher called on the Department of Parliamentary Services to immediately publish the five-year Conservation Management Plan and Design Principles for Parliament House, which was for release in 2016.
He said the public had a right to know whether other methods for achieving security outcomes had been comprehensively canvassed.
Mr Maher raised concerns the usual National Capital Authority public consultation processes would not proceed due to security issues.
He said the Department of Parliamentary Services appeared to have "abandoned its own processes for properly managing Parliament House".
'In 2014, the Department of Parliamentary Services committed to preparing a five-year Conservation Management Plan and Design Principles to manage this highly significant building," he said.
"An eminent expert advisory committee was commissioned to guide and finalise these documents. To date, no documents have been released.
"The work of this committee has reportedly been put on hold and Richard Johnson's design principles report rejected, which further adds to our concerns about decisions being made without the professional advice of distinguished architects."
Fairfax Media understands the controversial fences will be covered with foliage to lessen the visual impact to architect Romaldo Giurgola's original design, while one MP said the fence would be "almost at street level", a reference to Parliament Drive, which rings the building.
Construction is due to begin over summer.
Mr Maher said the fence proposal was flawed and posed a threat to the heritage value and design of the nationally significant building.
"Security requirements bring into conflict the two core principles of keeping people safe while at the same time allowing them access to the building and grounds. A balance must be struck, but the current proposal fails to deliver on both fronts," he said.
"This latest proposal to erect a 2.6-metre high perimeter fence will fundamentally change the character of the building and its symbolism as the people's house."
In a statement, the Department of Parliamentary Services has previously said the public would continue to have access to a significant amount of the grassed area on the northern side of the building. The speed of security checks at the main entrance could even improve.
The institute has requested that further information be released to bolster discussion about less intrusive options to enhance the security of the building.
"It is essential that on behalf of the Australian people, the fabric and intent of the design of Parliament House is protected now and into the future," Mr Maher said.
"Any change must be well considered and be consistent with the quality and durability required for a building of such status."
Hundreds of people rolled down the famous grassy slopes of Parliament House on Saturday for one last time before access to the lawns is blocked.
Plans are also under way to increase capacity inside the building, with a possible extension of the ministerial wing and the relocation of assistant ministers' offices.
A draft accommodation review considers additions to the building and the use or construction of buildings not connected to Parliament House.