The Government hopes the project will relieve the housing shortage in the South-East by providing 120,000 new homes over 12 years. Most development should be on brownfield - or previously developed - sites. But the Campaign to Protect Rural England said that even the amount of greenfield development permitted by the Government - up to 20 per cent - was too much and called for a ban. In its report, Thames Gateway - Making Progress, the CPRE called the Government's position "perverse".