Tom Heap investigates whether eco-cities are living up to their promise.

In years gone by, Costing the Earth has visited two eco-cities, which both promised that rapid urban development could be green, sustainable and profitable. Dongtan in China was meant to be part of "the quest to create a new world", according to British designers Arup. Masdar in the Arabian Gulf was to have "changed the world", according to British architect Norman Foster. But Dongtan never got built, thanks to Chinese political machinations and corruption, while Masdar has stalled, a victim of the world economic crisis.

China is still pressing ahead with over 100 new eco-cities. But does the idea of the eco-city make sense anyway? Critics say that some very ordinary new cities are being branded as "eco" in an attempt to give them a green marketing gloss, and that promoting the idea of the virtuous self-contained eco-city can mask a failure to build sustainably in the rest of the economy.

Producer: Jolyon Jenkins.