There is a remarkable sense of déjà vu in the debate about high buildings. We have been here before, but on previous occasions the more extravagant proposals evaporated as our economic fortunes dipped.

Tall buildings clearly make money, at least for a few people. Property owners, developers and a few architects are, not surprisingly, great enthusiasts. But for the rest of us the justification has still to be made. Higher densities are needed to minimise development on greenfield sites. But as Richard Rogers pointed out in Towards an Urban Renaissance, the report of the Urban Task Force, higher density development does not necessarily mean high rise. Some of the highest densities can be found in low-rise areas of elegant terrace housing, like Islington and Kensington, which have become celebrated centres of high-density living without sacrificing environmental quality.

Nor is there any reliable evidence that London's commercial future is dependent on tall buildings. Detailed research by the former London Planning Advisory Committee, and endorsed by the Government only 18 months ago, failed to find a need for high buildings to enhance London's importance as a world city. Indeed, over the past 20 years London's prosperity has been sustained by highly efficient, low rise "ground scrapers" of eight to 10 storeys, like the new Merrill Lynch HQ in the City of London.

The Manhattan factor has seduced cities all over the world into believing that for commercial success they need very high buildings. In Manhattan or Hong Kong, geography determined the need. But in London, Paris, Rome and even Berlin, there is a different European urban model, one based on organic growth over a long period of time, bequeathing complex layers of urban life deeply rooted in history. This has provided an economic dynamic more powerful than tall office buildings can generate. Much of the evidence suggests that tall buildings can severely prejudice this.

How many of the very tall buildings that we have today can really be regarded as breathtaking adornments to London's skyline? One of their principal failings has been that far too many were designed with a lack of appreciation or understanding of the context in which they sit.

London's Royal Parks and low-rise neighbourhoods largely rely for their amenity on an illusion of space which can easily be devastated by tall buildings looming over them. Is Hyde Park really a better place for being overlooked by the Hilton Hotel or Knightsbridge Barracks?

Should we care? If people want high buildings, why shouldn't they have them? Individual boroughs are competing for a slice of the action, but to scatter tall buildings across the skyline in the interests of competition between one part of London and another would destroy forever many of the qualities that Londoners and the world enjoy. We cannot afford to kill the golden goose for the sake of short-term expediency. If we do need tall buildings, it is essential to work out on a London-wide basis where they might go.

Paris, one of the most glorious low-rise cities in the world, has successfully grouped its very tall buildings at La Defense and Montparnasse. London has the opportunity to do the same at Canary Wharf and, perhaps, one or two other centres. But one of the opponents of the growth of Canary Wharf is the City Corporation, the guardian of London's oldest financial quarter, which fears that the centre of economic activity will move east to Docklands. But so what if it does?

English Heritage is not opposed to high buildings ­ as long as the case has been made, the buildings are world class and, above all, in the right place. That is why we supported Norman Foster's "erotic gherkin" for the Baltic Exchange site, an outstanding piece of new architecture which provides a coherent focus to a random cluster of existing tall buildings. Conversely, we have opposed the Heron Bishopsgate Tower because it is an unexceptional building in the wrong place which damages the world-famous prospects of St Paul's from Waterloo Bridge and the newly-opened terrace of Somerset House.

What is needed is a strategy. That is why earlier this week we launched joint national guidance on high buildings with the Commission for Architecture and the Built Environment, and why we are urging Mayor Ken Livingstone to ensure that a sophisticated Spatial Development Strategy for the capital reinforces the qualities which make London special as a world city.

Prior to his election, Ken Livingstone described English Heritage as "the conscience of the mayor". English Heritage firmly believes that London has unique qualities of cityscape that provide the true measure of its past success and its future prosperity. The Canaletto effect is at least as powerful as the Manhattan syndrome, and far more relevant to London's long-term needs.

The writer is the Chief Executive of English Heritage