Metropolitan plans matter. Good ones direct investment efficiently, protect a city's greatest assets such as amenity and the quality of the environment, and help lessen inequality. They create a culture of certainty essential to economic success by promoting long-term public and private investment. Everybody knows the plan and works to it over a long time frame. Where they don't exist, cities are more likely to fail, such as many American cities afflicted with fragmented systems of government. Melbourne is still benefiting from the strategic thinking of former premier Sir Rupert Hamer and the Melbourne and Metropolitan Board of Works. Unless we rediscover effective urban planning quickly, Melbourne will cease to function effectively with dire consequences for its citizens. The Victorian government has radically deregulated its land use planning system, giving unprecedented power to developers to determine the shape and function of our city.

Having largely given planning away to private interests, the government is not going to take it back through a powerful metropolitan plan. The 2013 plan's most serious failure is that it does not redirect transport spending from roads to public transport and link this to land use. No government now has credibility on infrastructure spending promises. But this is a roads strategy. Its promises to deliver new suburban rail lines and the Melbourne Metro are unfunded and unbelievable. Without a radical extension of public transport, Melbourne cannot work as the city of 6 million to 8 million people the government wants, but will descend into dysfunction. Unless we rediscover effective urban planning, Melbourne will cease to function effectively. The government proposes to retain the primacy of the central city, and to foster economic growth in connected metropolitan regions, employment clusters, large-scale redevelopment areas and activity centres. It wants also to foster development in some nearby rural towns. But there is little logic in the choice of growth areas, no funding for infrastructure. These proposals are full of contradictions and are so vague as to be of little use.

Extensive redevelopment will certainly occur, but not guided by this plan. Large parts of Melbourne are becoming high rise already. The heritage values of the central city, Victorian-era strip centres, commercial and mixed-use areas and their residential environs, and arterial roads will be destroyed by high and medium-rise development. Planning Minister Matthew Guy will not admit to a policy that so fundamentally changes Melbourne's shape, character and functioning because then we would know what he is up to. Melbourne 2030 sought to redirect a large proportion of outer urban growth to the established city through a legislated urban growth boundary. However, it never resolved how to protect heritage and amenity while concentrating development in mixed-use centres. The 2013 strategy now proposes a fraudulent limit on outer urban sprawl, a fake policy since the Liberal-National parties in 2010 helped destroy the former growth boundary by expanding it by 43,000 hectares, making irrelevant any contrived limits to growth. A metropolitan plan should begin with a city's great assets and protect them.

This century, cities that protect their built heritage, and the amenity and the resources of their hinterlands, will be best able to adapt and survive. Urban heritage is the basis of the city's identity, liveability and economic success. Melbourne's green belt is Victoria's second most productive agricultural area. But the government will open up much farming land close to Melbourne for major tourist, accommodation and other commercial uses. Normally, a metropolitan strategy sets the direction, and the planning system, including zones, conforms. In Victoria, the opposite is true: new planning zones are the real strategy, most enabling a wide variety of uses and developments, many without permits or resident notification. This means that the strategy must be weak. The big retailers now control almost 40 per cent of retailing and most supermarket sales. A metropolitan plan should revitalise small business in strip centres, but cannot because commercial zones promote dispersed retailing in malls and big-box stores. Increased inner urban populations will be forced to travel by car to these dispersed centres.

The interests of big retailers, road builders and developers are not necessarily ours. That's why we need government. This government has no idea about how to promote affordable housing. Melbourne will continue to grow as two city types that entrench unequal access to the best a city can offer. Well-serviced inner and middle-ring areas will become more exclusive, while sprawling new suburbs will condemn many outer residents to the worst standards of infrastructure and facilities. Cities fail when powerful private interests are allowed to determine the future, advantaging a few in the short term at the long-term expense of the many. This new plan, regrettably, has set Melbourne on the path to failure. Michael Buxton is Professor of Environment and Planning at RMIT University.