As part of their rather strange campaign against the Brent Council Civic Centre, members of the Green Party have criticised the carbon costs of constructing the building. Of course, they don't try to source any figures for this, merely assert it.
In fact as part of the BREEAM process, the construction is monitored to minimise carbon emissions. Hence materials are locally sourced wherever possible, and Skanska employ sophisticated building techniques to minimise "embodied carbon". For example, the concrete is a mix of Portland cement and blast furnace slag that reduces the embodied carbon by about a third.
As far as I can see, Brent Green Party would have preferred Brent Council to concentrate resources on maintaining as big a building portfolio as possible regardless of the suitability of the buildings, or the higher rate of carbon emissions.