But the Eco-town Challenge Panel, a group of experts appointed by government to assess the bids, was largely positive about the changes bidders had made to their proposals in response to a previous, critical report from the panel.
The panel said the Tesco-backed proposal for an eco-town at Hanley Grange in Cambridgeshire was in danger of "becoming a dormitory town for London commuters" because it had not implemented the panel's recommendation on a dedicated busway and bicycle links and placed emphasis on the use of a local station.
However there was praise for its idea for a resident-led community trust to govern the town and ensure standards are maintained.
It also said North East Elsenham in Essex would find it difficult to become zero carbon because its proximity to the M11 could encourage commuting.
The panel said Weston Otmoor in Oxfordshire needed to work out how the town should be governed - it recommended a community trust.
Pennbury's transport infrastructure needed to connect better with Leicester and the bidders should look at creating more jobs in the town to reduce the need for residents to travel to work, the report added.
Several of the eco-town proposals needed to say more about how they would reduce residents' carbon footprints from the average of 12 tonnes to the 2 tonnes, the panel urged.
Housing minister Caroline Flint said: "The progress made over the past few weeks demonstrates the willingness of the promoters to react to the expert advice they have been given. But there are no done deals and only the best quality schemes with very high sustainability standards will qualify for eco-town status."