Roisin Shortall, the Labour TD for Dublin North West, is not alone in wondering how a handful of people - mostly from outside the area - can hold up, and perhaps even jeopardise, the £250 million plan to redevelop Ballymun.

The plan to create a "model town for the 21st century" is in jeopardy because of planning appeals lodged by Friends of the Irish Environment, in the name of Peter Sweetman, a former Green Party activist based in Borrisoleigh, Co Tipperary, and a judicial review sought by Robert Guillemot, a Breton musician who lives in one of the tower blocks.

Ballymun Regeneration Ltd, the Dublin Corporation subsidiary set up to oversee the project, is exasperated by these challenges. It fears that the uncertainty they have created and the inherent delays in processing them could deter much-needed private-sector investment, particularly in the new main street.

Mr Guillemot, who is away at present, is said to believe that the entire plan is misconceived. In his view - and he is said to enjoy a spectacular view of the Dublin Mountains from his high-rise flat - the idea of razing all of the 1960s blocks in Ballymun to make way for a sprawling low-rise housing estate makes no sense in terms of sustainable development.

Since this thesis runs counter to both the policy of getting rid of all the system-built blocks and the master plan to redevelop the area on a "human scale", there was no mechanism for advancing it at an earlier stage. Thus, the objectors were left to cherry-pick individual housing schemes in the first phase for planning appeals or judicial review.

Tony Lowes, one of FIE's co-ordinators, complains that there was no environmental impact assessment (EIA) of the Ballymun scheme. But then, how could such an assessment be carried out when most of the new buildings have yet to be designed? All we have seen so far are designs for 620 new homes and an arts centre on the new civic plaza.

"This project has been subject to the most extensive consultation and it is supported by the majority of people in Ballymun", says Rois in Shortall. "Everyone was expecting that the JCBs would be on site this autumn, but now there's a danger that people could lose faith in the whole process because of the actions of a small group of objectors."

But Mr Lowes insisted that the project was "not being held up by foreign troublemakers". He pointed out that Mr Guillemot had lived in the flats for 20 years and said that FIE had received "a lot of support from within the community, from people who disagree with the plan to demolish everything that stands there".

Mr Lowes, who wears another hat as chairman of An Taisce's Natural Environment Group, grew up in Britain and the US and has been an Irish citizen since 1967; he lives in west Cork. On occasion, his activities have resulted in threats being made against him by developers and their supporters, who regard him as no more than a troublesome "blow-in".

Another FIE founder-member is Dr Sara Dillon, a US-born law lecturer at UCD, who believes passionately that irreparable damage is being done to Ireland's environment by the present economic boom. She got involved in setting up FIE because of the need for a specific group to monitor Irish compliance with EU environmental legislation.

FIE works closely with Lance fort Ltd, the company set up by Michael Smith, chairman of the Dublin city branch of An Taisce, to fight high-profile planning cases. Its longest struggle was with Treasury Holdings Ltd over the controversial plan for a Hilton (now Westin) hotel at College Street, involving extensive demolition and facade retention.

Here again, one of Lancefort's main complaints was that the hotel scheme had not been subjected to an EIA, despite its huge environmental impact. Now, ironically, a Treasury Holdings subsidiary is using the same argument in its case for a judicial review of An Bord Pleanala's decision to approve plans for another hotel scheme in Parnell Street.

Keelgrove Ltd, the Treasury subsidiary involved, owns a site in the area which it sees as having a "strategic nuisance value", according to the minutes of a meeting between its principals, John Ronan and Richard Barrett, and Paul Clinton, project manager for the proposed Millennium shopping mall on the Carlton site in O'Connell Street.

Not only did Keelgrove seek a judicial review of the Parnell Street hotel scheme, it also appealed against the Millennium mall, and it may go to the High Court again if An Bord Pleanala approves the plan. Thus, it can be seen that the planning laws may just as easily be used as a vehicle by developers seeking to get their own way as by conservationists.

It is unlikely that the Construction Industry Federation and others who fervently favour limiting third-party rights under the planning laws would have the likes of Keelgrove in mind. Along with IBEC and IDA Ireland, the CIF is lobbying for restrictions on objectors in legislation to be published shortly by the Minister for the Environment, Mr Dempsey.

His Department is well aware of the difficulties caused by individuals asserting their rights. The remaining Southern Cross section of the M50, for example, was held up for nearly three years by two local landowners, Maj T.B. McDowell, chairman of Irish Times Trust Ltd, and Mr Edward Fitzachry, and by the Select Vestry of Whitechurch.

Settled out of court on terms which have never been disclosed, their legal action has since resulted in the creation of a huge artificial mound to screen the properties of those involved from the sight and sound of the motorway.

Meanwhile, Mr Lowes is locked in another battle over the Kildare by-pass, which An Taisce fears could de-water Pollardstown Fen, the most important aquifer in Leinster. Its complaint to the European Commission is being treated very seriously; at home, however, it has been ridiculed as being about the "protection of some snail".

A small group of environmentalists, admittedly with wider public support, is still fighting plans for visitor facilities near Mullaghmore, in the Burren. Their most important victory came in 1994, when the Supreme Court ruled that the State was not, after all, exempt from going through the normal planning process.

The Department of the Environment is now planning to introduce the EU-inspired concept of Strategic Environmental Assessment (SEA) on a pilot basis for major plans and/or policies. Had such a mechanism been available, it would almost certainly have shown up some of the dangers inherent in the notorious Seaside Resorts tax incentive scheme.

Based on the physical evidence of what's been built, notably the endless clusters of suburban-style holiday homes, the environmentalists have been proved right in their early criticisms of the scheme. Unfortunately, the same is likely to prove true of the Upper Shannon designated area, which also seems destined to be littered by this type of development.

Public authorities seeking to get things done will always find objectors irritating. Dublin Corporation has been thwarted by a successful High Court action by Micheal O Nuallain, a brother of Flann O'Brien, over the 120-metre millennium spire for O'Connell Street; an EIA must now be undertaken and new approvals issued before it can be built.

The city manager, John Fitzgerald, has asked whether the right balance has been struck between individual citizens and public authorities in terms of environmental protection. He asks: "If every major project is to be judicially reviewed after going through the planning process, how are we to deliver anything on time?"

Tony Lowes stoutly defends the objectors. "It's never down to a single individual. Somebody's name may go forward, but there's always a group behind it", he says. In the case of Ballymun, FIE is behind Robert Guillemot. "He wouldn't have known where to get a lawyer if it wasn't for us. But we wouldn't have a leg to stand on if there had been an EIA."