New plans for the radical mixed-use redevelopment of London's Grade II-listed Commonwealth Institute building in Holland Park have angered heritage groups.

The designs have been submitted to the Royal Borough of Kensington & Chelsea Council (RBK&C) by the Office of Metropolitan Architecture (OMA), with the intention of converting the building into a possible new home for the Design Museum. The redevelopment, led by developers Chelsfield Partners, includes the removal of the administration building and extending the basement for retail, restaurant and café uses. In addition it also proposes the construction of a mixed-use building to include a cinema, fitness centre with swimming pool and spa facilities along with two residential buildings to house 72 units.

Heritage and local campaign groups are outraged by the developer's apparent failure to retain much of the original 1962 design. The project would remove or significantly alter the existing floor level of the main building, the ancillary block, the flagpoles, walkways and interior void. Twentieth Century Society (C20 Society) in particular is "disappointed that OMA have not risen to the challenge of combining innovative new architecture and sensitive refurbishment", or taken the advice it and Heritage England provided pre-application.

A spokesperson for C20 Society said: "The planning application states that the brief will allow for 'the Design Museum or some comparable institution' to occupy the altered building. All the other significant areas would be destroyed. This is not a satisfactory, conservation-led approach for a Grade II-listed site of international importance that is also a registered park and garden in a conservation area. The C20 Society, in conjunction with The World Monuments Fund, SAVE, The Edwardes Square Scarsdale and Abingdon Association, have commissioned a conservation assessment for the site by the Architectural History Practice. The report, which presents a recent assessment of the site, concluded that "any proposals for development should start from the premise that the whole of the present building and its setting is significant and the utmost care should be taken to preserve as much as possible of that significance".

A public consultation on the plans is due to start today and end 22 May 2009, and C20 Society plans to make a "proper representation to RBK&C".