Heritage and architecture supporters have banded together to file a federal lawsuit against the proposed memorial to victims of communism, one day after the National Capital Commission unveiled plans for a smaller, less-intrusive version of the controversial monument.

The lawsuit is being sought by the Royal Architectural Institute of Canada, who had previously spoken out against the monument, as well as local group Heritage Ottawa and architects Barry Padolsky and Shirley Blumberg.

In a statement, the groups allege the NCC violated its own public consultation procedures as well as the National Capital Act in its "hasty" decision to begin preparations to decontaminate the memorial's site despite not having a finalized design in place.

​They are asking that Thursday's decision by the NCC to decontaminate the proposed site of the memorial, located between the Supreme Court of Canada and Library and Archives Canada, be quashed, and that the NCC be temporarily prevented from breaking ground at the site.

They add that they "do not oppose the commemorative intent of the memorial."

The revamped memorial design, also unveiled Thursday by the NCC, would reduce the size of the memorial from covering 60 percent of the approved site to only 37 percent.

As well, the height of the memorial would shrink from 14.35 metres to eight metres.