Lewis was responding to the announcement that urban design consultancy URBED had won the £250,000 Wolfson Prize for economics, for its template for the development of garden cities (92-page / 15.1 MB PDF) across England. URBED argued in its winning entry that the most sustainable way to build new garden cities was to expand existing "mature towns", with all the infrastructure and facilities required for a thriving city already in place.
The authors called for the next government to bring forward legislation enabling existing towns to apply for garden city status. Successful bidders would receive financial support and land acquisition powers, to allow them to build large sustainable extensions within 10km of existing town centres, connected to the town by new tram lines or bus services.
URBED said that such a plan would require taking "a confident bite out of the green belt", but that "for every hectare of land developed another will be given back to the city as accessible public space, forests, lakes and country parks – the garden in which the city will sit."
In a statement following the announcement of the prize, Lewis said: “We are committed to protecting the green belt from development as an important protection against urban sprawl. Today’s proposal from Lord Wolfson’s competition is not government policy and will not be taken up.” Although the URBED proposals envisage the garden city application process to be of a voluntary nature, Lewis said that the government did not "intend to follow the failed example of top-down eco-towns from the last administration”.
According to a report in the Independent, David Rudlin of URBED responded to Lewis comments, and said: "We have to build on the green belt. Ignoring it is not an option. This notion that you are building over everything isn’t really true. If you draw the area you require, it surprised me how little space you need to expand cities of this scale."