After a century in which cities were treated as problems - dirty, crowded, dangerous - the 1997 general election marked a turning point with a new government that saw cities as the only sustainable solution to the growing demand for housing.There has been a measurable cultural shift - to an understanding that we need to use land better, and plan better, to sustain our cities. If you visit Manchester today, you can see tangible evidence of that change in the centre. Over 15 years the population has soared from 90 to 25,000, bringing life and pride back to one of our great urban centres.
But if you travel just a few blocks from revitalised city centres you can see shoddy housing and wasted land, which shows how many problems remain. Most worrying are the signs that the government is losing its nerve: that it is beginning to focus on quantity at the expense of quality.
The greatest danger is that the government might weaken its policy of giving priority to development on derelict brownfield sites. This sequential approach to land use is crucial to strengthening the social and economic vitality of the city and protecting the beauty of the countryside.
When you review the facts, there is no need to abandon a commitment to brownfield development. The total quantity of brownfield land has fallen by only 3% over five years, and the housing capacity of the land that remains has actually grown by 7%. This supply could be boosted by more responsible use of publicly owned land, if the potential regeneration value of redundant military, NHS or rail property were taken into account. Focusing on market value alone seriously undermines our ability to regenerate cities.
Brownfield development will always be difficult, but there are other barriers to tackle. The fiscal framework for development also needs attention; it is no surprise that house builders are lobbying for access to greenfield sites when the development costs are so much lower. The government should review the fiscal framework to make the true costs of greenfield and brownfield development more equitable.
Good urban design is about paying attention to the spaces between buildings as well as the buildings themselves. Well-designed streets, parks, squares and pavements are the scene for the synthesis of urban life. If you make streets attractive to passersby, then you enhance quality of life and security: busy streets police themselves. Citizens should be able to enjoy well-designed public spaces at all scales, from small quiet gardens to squares, parks and countryside easily accessible on foot or public transport.
We can all recognise beautiful family-friendly neighbourhoods, be they leafy Georgian terraces or the new waterfront developments in Amsterdam and Barcelona. We must all ask why we cannot aspire to this quality of development for all. Architecture is not just aesthetic; it has social, moral and political dimensions. Badly planned and maintained spaces and buildings play an important part in brutalising people.
Urban renaissance needs to spread out beyond our city centres. Most of our city-centre population growth consists of young and single people. To draw families back to cities, we need to create beautiful and family-friendly suburbs too. Architects and planners have often neglected, or even derided, suburbs. They may lack the urban vitality and mix many of us enjoy, but they provide a quieter, greener environment for families and can enhance the mix of housing that a city can offer. The best suburbs - linked to the city by good public transport - already offer a model for a different style of environmentally sustainable urban living. We need to bring all of them up to this standard, through intensification and new infrastructure.
But to make our suburbs work, you need intelligent and design led planning. One only has to look at the dreadful suburban strip that stretches along the Mediterranean coast from the south of France to Spain and Italy, let alone the sprawl outside our own cities, to realise how important it is to use our planning laws intelligently, not to let rip.
The debate over use of greenfield and brownfield land is not really a debate about saving green space from development, but a debate about the future of our cities, about saving them from physical dereliction, social fragmentation and economic decline. We must continue to choose a more sustainable urban form of development, which minimises car use and maximises access to local shops and services within walking or cycling distance - and provide good public transport to enable travel over longer distances.
The urgency of climate change makes the urban renaissance crucial to the survival of our planet as well as our cities. This is not the time to lose our nerve.
Richard Rogers is chairman of Richard Rogers Architects, and chairs the government's Urban Task Force.