When DEGW, the London architects and urban designers, was appointed by Dublin Corporation last December to examine the contentious issue of high-rise buildings, it was asked to "consider critical views across the city skyline" and to recommend "preferred locations" for landmark buildings.

But Prof John Worthington and his team, in the course of their six-month study, appear to have broadened the terms of reference to embrace the question of what kind of Dublin we want to see and then passed the whole issue of high-rise buildings back to the planners, the politicians and the population in general.

Dublin itself, says DEGW's 78-page report, "needs to decide how far and in which way single high-rise buildings can contribute to the development and image of the city before specific locations can be identified". And what is "fundamental" to such a change in character is political will, combined with "widespread public support".

Character is a word that occurs frequently in the DEGW study, entitled "Managing Intensification and Change: A Strategy for Dublin Building Height". Its authors helpfully divided the city into an elaborate series of "character areas", ranging from the "set-piece" southside Georgian core to large "brownfield" sites in the Docklands area.

The aim was to define the potential for increases in density and building height, taking into account such issues as architectural conservation, land ownership and relative accessibility in the broader context of urban design. Hence, as the authors say, the issue of high-rise buildings is "more than simply an aesthetic or skyline consideration".

In general, the report argues, Dublin should aim to retain its intrinsic character through a policy of incremental change, "whilst allowing for large-scale growth and innovation in building form at strategic locations". High buildings "should be the exception rather than the rule", not least to avoid diluting their impact as new city landmarks.

The biggest constraint in devising a fully co-ordinated policy, as the report notes, is "the lack of a clear regional transport plan". Before the latest version of such a plan was unveiled by the Taoiseach on October 2nd, it said there was "very little information" either on the likely capacity of the rail services proposed or on the location of new stations.

Higher density development must be located in the vicinity of public transport nodes, otherwise it would become a car-dependent disaster. Any further increase in traffic congestion, with no improvements in public transport, "will inevitably compromise" the city's attractiveness as a location for large-scale commercial activity, it warns.

By comparison with Amsterdam, Copenhagen and Lyon - the three cities against which Dublin is "benchmarked" - the absence of an integrated public transport network to stimulate development, according to the authors, puts Dublin in "a fortunate position to reflect on the experience of other cities and decide on an appropriate future".

Relying on an earlier version of the DTO's regional transport plan, the report identifies three potential locations for new "high-activity clusters" - Spencer Dock, Broadstone and Heuston. However, the report says the development potential of each location will vary due to such factors as character, context and the availability of land.

What DEGW argues is that "consistency in approach would be inappropriate". In a city experiencing significant growth and change, "controlling height through blanket height and zoning regulations is neither appropriate nor productive within the context of current development practice". Thus, a more varied skyline policy is required.

Skyline formation could not be "appropriately addressed" through the designation of protected views. Protection of specific views should be designated only in relation to set-piece conservation areas, such as the Georgian Mile and Trinity College. Elsewhere, policy should "not preclude the possibility of high-rise buildings when appropriate".

Noting the city has "a conservative planning and property regime", the report says Dublin Corporation should clarify its objectives and focus on being "strategic, pro-active and visionary" by setting down planning goals, identifying critical parameters, stimulating new development in areas where it is warranted and preparing development briefs.

Its 10-point strategy also aims to "intensify existing activity clusters" and mentions the IFSC and Temple Bar in this context; whatever about the former, it is hard to imagine how the latter might become more "intense". Within other "character areas", it says "carefully considered" high buildings might be allowed to create more diversity.

The report points out that "high building" is a relative term. Thus, Liberty Hall is a high-rise landmark in its context whereas the apartment tower at Charlotte Quay, though only 13 metres (43 ft) lower, "sits quite comfortably in its surroundings". Similarly, a five to seven-storey block would make quite an impact in any of the low-rise suburbs.

But the authors caution against prescribing very high densities in selective locations, because of the danger that this could "syphon off" demand for other areas by sterilising or greatly limiting their development potential. It also points out that freestanding towers have "significantly less capacity" to increase floorspace than, say, slab or terraced forms.

And while DEGW describes Dublin as "a city of world ranking" because of its burgeoning growth, its potential for developing very large-scale high-rise clusters outside the urban core, such as London's Canary Wharf or La Defense in Paris, would arise only "if and when" the city becomes a metropolis of three million - not an imminent prospect.

Nonetheless, it is estimated that 24 million sq ft of new office space could be built in Dublin over the next five years or so. Of this total, 2.84 million sq ft is under construction, 7.8 million sq ft has outline planning permission, 3.4 million sq ft is going through the planning process and 9.9 million sq ft is at pre-planning stage.

Of the total floorspace, an estimated 6.6 million sq ft is likely to be located in the Docklands area. Here, however, the report is curiously biased towards the southside, saying towers of up to 15 storeys could easily be accommodated in the Grand Canal Docks area while a general height of four to nine storeys is suggested for the north Docklands.

"Height controls will need to be considered on a site-by-site basis to ensure critical views are maintained and the quality of conservation areas is not compromised", it says, adding that the area around Heuston Station has potential for well-designed buildings of up to 40 or 50 metres in height (132 to 165 ft) "without compromising the local context".

Other possibilities include "gateway" sites or focal points that capture "long views across city-wide corridors" such as the Liffey, or the vistas south from Mountjoy Square towards the Custom House or east from Henry Street towards Connolly Station. Long-term prospects might include the Poolbeg peninsula and other Docklands sites.

Based on continental experience, one of the potential threats DEGW identifies is "the cloning of inappropriate models" from North America which are out of scale with their context - as exemplified by Kevin Roche's master plan for Spencer Dock, though this is not mentioned in the report. A design-led app roach, preferably by competition, is favoured.

According to the authors, the onus should be on developers and their architects to "test and prove that the conditions are acceptable" for any high-rise building. And, unlike the massive bulk of the failed Spencer Dock scheme, their preference is for "slender tower forms" with elegant skyline profiles and well-designed outdoor spaces at ground level.

Quite apart from impacts on the skyline, conservationists consulted by the study team felt the comprehensive development of high buildings represented "the appropriation of the city" by private developers. "Few see a positive need for high buildings. The pressure is seen to emanate from `the pride of architects and the greed of developers' ".

As for the impetus to reach for the sky, DEGW says "from the 13 medieval towers of San Gimiano to the twin Petronas Towers in Kuala Lumpur, the desire for presence and domination is still a strong objective" - even though, as the report candidly concedes, this is "often only achieved at the expense of good city form and environment".