Dublin car park owners say high-end retail trade could suffer a 24% drop if proposed traffic restrictions are imposed in the core city centre.
A survey for the Irish Parking Association found that nearly 60% of shoppers who drive into Dublin said they would stop doing so if they could not take their car.
Car park owners warned that such shoppers could avoid the city centre if plans go ahead to restrict private cars from the College Green area and parts of the quays.
The car park owners commissioned a Red C survey, which concentrated on high-end retail customers and found 41% were car users.
Of these, nearly three out of five said they would not go into the city if they could not use their car.
The survey comes as further restrictions are imposed on private motorists at College Green because of Luas works.
The bus gate is now operational 7am to 7pm Monday to Friday.
One of Dublin's leading retailers has said city authorities should consider alternate traffic routes or congestion charges to relieve gridlock, rather than seek to ban private cars from parts of the city centre.
Speaking on RTÉ's Morning Ireland, Arnotts Chief Executive Ray Hearnan said the proposed measures are attempting to force people to use public transport and many motorists will simply choose to go to suburban shopping centres.
Mr Hearnan said he accepted there was an issue with traffic congestion at peak commuter times, but said these proposals would ban access to private cars around the clock.
He said the National Transport Association and Dublin City Council should consider alternative options.