The eminent 89-year-old Italian-American, who became an Australian citizen and settled in Canberra after Parliament House was completed, said the new headquarters' linear design was a mistake which massacred the National Capital Plan, the strategic plan for Canberra and the territory.

Dr Giurgola is torn over criticising the headquarters because an off-shoot of his practice, Francis-James Morehen Thorp, is the architect of the contentious new $600 million project.

He said buildings in keeping with Canberra's first architect Walter Burley Griffin were of discrete volume, allowing people to see past them to Parliament House and Lake Burley Griffin.

Constitution Avenue had modest-sized school, church and office buildings, whereas ASIO's big facade was the wrong shape in the wrong place, in contrast to Parliament House which was open to the public.

''Anybody can go inside and it is very healthy in terms of an office building.

''That is the kind of architecture that should be here you know not this monster.

For more, pick up a copy of today's Canberra Times