The assessment is a major setback to plans by the Swedish company, which submitted a planning application last February and hopes to open its doors early next year.

Ikea wants to build a 30,000sq m store at Ballymun which would directly employ 500 people and create another 100 outsourced jobs. Environment minister Dick Roche changed the retail planning guidelines specifically to facilitate large outlets like Ikea.

There are now fears in the Ballymun area that the official criticism may lead Ikea to consider other locations.

Documents released by Fingal County Council show that the National Roads Authority (NRA) has emerged as a leading critic of the project. The NRA is concerned about the detail in Ikea's planning application, in particular the traffic impact assessment which is said to "underestimate the potential car trips to and from the development".

Despite Ikea's plans to have 1,500 car spaces, the NRA believes "the current proposal is likely to provide inadequate parking and carry a high risk of extensive traffic queuing extending onto the M50".

The council planners also concluded that Ikea had underestimated the potential success of its store at the Ballymun location.

In its planning application, Ikea promised to introduce a subsidised home delivery service for customers who use public transport. Further information about this service has been sought, while planners have suggested Ikea consult with bus companies about "extending public transport services to the development".

The planners also said they had "serious concerns" about the impact of the development on retail centres at Blanchardstown, Liffey Valley and Ballymun. Ikea now has six months to respond to the council's request for additional information about the project.