The scheme for Spencer Dock, according to one of its many detractors, makes Liberty Hall look like a telephone kiosk. Another critic, admittedly a prospective neighbour, said it would be like living next door to the Cliffs of Moher with windows.

Such colourful epithets convey a sense of the enormous scale of what is undoubtedly the biggest urban development proposed in Ireland - a whole mixed-use urban quarter with 6 million sq ft of floorspace on the most important site in Dublin's Docklands.

If this mainly CIE-owned 51acre site was overlaid on the city centre, it would extend from College Green to Harcourt Street. At more than twice the size of the designated Temple Bar area, it also accounts for a quarter of all the developable land in Docklands.

For everyone who attended An Bord Pleanala's oral hearing, the image that will stick in their minds is a 1:1,000 scale model of the entire swathe of Dublin from Liberty Hall to the Point Depot, extending southwards to Merrion Square and northwards to Mountjoy.

This model, which showed every building north and south of the Liffey in block form, was requested by the appeals board to illustrate the huge scheme for Spencer Dock in context, so that it might be able to assess its impact on the generally low-rise skyline of the city.

What the model did was to answer the fundamental question about this development: "How big it is, or how big is it in relation to everything else?" as Dublin architect Sam Stephenson, who gave it his personal endorsement, once wrote about Kevin Roche's work.

Supplementing the 1:1,000 cityscale model was a plethora of photomontages and other computer-generated images as well as a white, cardboard block model of Mr Roche's master plan and two more refined models of his National Conference Centre.

This was the prize which the eminent emigre architect, now away from Ireland for more than half a century, had returned home to collect - a commission to design a major public building on the Liffey, joining the Custom House, the Four Courts and the Civic Offices.

Unfortunately, because of the preference of successive governments for the National Conference Centre to be built and run at no cost to the State, Mr Roche's office in Hamden, Connecticut, had to create a master plan for a massive commercial development to support the loss-making centre.

The scheme for which planning permission is being sought is the 35th version worked up by the architects. But given their clients' insistence on the magic figure of 6 million sq ft, the architectural exercise was akin to moving draughtsmen around a checkered board.

The developers, a consortium led by Treasury Holdings, tried without success to persuade the Dublin Docklands Development Authority to go along with the scheme before finally deciding, a year ago this month, to risk taking it through the planning process via Dublin Corporation.

In what seemed at the time like a Solomon's judgment, the corporation decided to grant full planning permission for the conference centre and one office block, subject to its height being reduced, and only outline permission for an overall 4.6 million sq ft on the site as a whole.

Even this was over-generous. The corporation's architectural adviser, Michael Lowe, conceded at the inquiry that it was based on "giving more value" to the developers rather than on purely qualitative criteria, backed up by a realistic assessment of what the site could "carry". The developers' team, led with gritty determination by planning consultant Tom Phillips, insisted that the corporation's permission was unworkable. But no figures were produced, not even the EU-ordered cost-benefit analysis of the conference centre. It remains "confidential".

We were addled by calculations of the scheme's plot ratio - the total floorspace divided by the site area. The developers' figure of 2.67:1 was derived by including streets, roads, campshires and even waterbodies within the red line and excluding the podium car park. Both Dublin Corporation and the Dublin Docklands Development Authority insisted that the true plot ratio was much higher: over four to one, according to the authority, compared to 2.27:1 on the 12-acre Financial Services Centre extension just west of Spencer Dock.

Certainly, the difference in scale is dramatic. The plot ratio argument, with several parties doing their own sums, may have been relevant in strictly planning terms. But John Martin, deputy city planning officer, was surely right when he described plot ratio as merely a tool; the height and bulk of the model told the story.

BY PERMITTING the developers to include the canal water body within the red line, after they promised that it would be "fully restored", the Minister for Arts and Heritage, Ms de Valera, allowed them some 500,000 square feet of floorspace, worth around £100 million. Yet the Waterways division of Duchas, the Heritage Service, which has responsibility for the Royal Canal, still has "grave reservations" about aspects of the scheme, including the overshadowing of Spencer Dock by the conference centre's largely blank gable wall, nearly 140 feet high.

The fact that Bord Failte, as commissioning agency for the conference centre, declined to give evidence suggested it was not prepared to defend a building more than twice the size of what its brief specified. Des Johnson, the presiding inspector, described this as "unhelpful".

Mr Johnson and his colleagues, Karl Kent and Gerry Barnes, conducted the hearing in an exemplary fashion. They knew all the right questions to ask and never ceased probing the core issues, particularly the many imponderables that swirl around this extraordinary scheme. Chief among them is the still unresolved strategic issue of the crossriver rail link southwards from Spencer Dock and whether it would run overground or underground. Attempting to get answers on this issue was, as Mr Johnson put it, "like trying to pick up mercury with a fork".

Then there is the fact that most of the 26 buildings have not been designed, rendering the notion that it should get full planning permission meaningless. Even its architect suggested that the scheme could be reconfigured if it was viewed as "catastrophic".

Before 77-year-old Kevin Roche took the stand, it seemed that Spencer Dock was going down in flames. And while the developers were delighted by his performance, the real question was how a man as nice as Mr Roche could have designed such a terrible scheme.

Apologists such as the architecture critic, Martin Pawley, suggested that its international-style "anywhere architecture" was justified by the need to meet the requirements of global capital - raising the issue of whether Dublin should trade its identity for inward investment.

Given that this was one of the central arguments put forward in favour of the scheme, there might have been more debate about it at the inquiry. But Mr Johnson cut short Councillor Ciaran Cuffe of the Green Party when he sought to argue that cities such as Dublin needed to assert their identity.

The most coherent case against the scheme was put forward by Dermot Desmond, no stranger to the world's money markets. An Taisce reckoned that the cost to him of engaging an impressive team of experts for the public inquiry exceeded its own annual budget of £140,000.

What was most striking about the hearing was the universality of the opposition, not just from Mr Desmond and his team, but also from docklands residents, conservationists, the Dublin Docklands Development Authority, Dublin Corporation, city councillors and, offstage, from the Taoiseach himself. Though Mr Ahern has since requested An Bord Pleanala to ignore his "monstrosity" remark, there can be no doubt it indicated clearly to everyone that there was no longer any high-level support for the Spencer Dock scheme, or even for the conference centre.

WHATEVER goodwill Treasury Holdings had was squandered by its squabbling with the docklands authority in 1998, its objections to other developers pursuing two major schemes for O'Connell Street and Parnell Street, and its more recent battle with the ESB. As for Treasury's partners, CIE, it is clear that the real-estate imperative of maximising density overwhelmed the resolution of public transport issues; it was particularly odd that its spokesmen saw no problem in providing nearly 7,000 parking spaces on the site.

But the "great leap forward" which the developers would have us take at Spencer Dock represents such a radical departure that it requires a municipal consensus. And that can only be achieved by preparing a publicly owned master plan for this mainly publicly owned site. The city skyline study commissioned by the corporation might well conclude that it could take a few high-rise buildings, even a tower or two. But that is very different to the great wall of tall bulky buildings now proposed.

If the Dublin Docklands Development Authority was to prepare a master plan for Spencer Dock, in consultation with the corporation and the public in general, the cleanest way of preparing the ground for it would be a straightforward refusal by An Bord Pleanala for the present overblown scheme.

Thus, returned to a blank canvas, it should be possible to find a better location on the site for the conference centre - addressing a public square rather that presenting a clifflike gable to the Royal Canal and surrounded by buildings with a scale more appropriate to Dublin.

Wisely, the appeals board has deferred its decision until after the skyline study is published in June. But if the Government really wants the conference centre, it should dig into its deep coffers to pay for it rather than allow Spencer Dock to be smothered by a profit-driven development.

fmcdonald@irish-times.ie