IHS Automotive forecasts that the UK's vote to leave the European Union could cost automakers about 2.8 million light-vehicle sales through 2018.
The research firm expects global deliveries to rise to 89.82 million this year, or about 200,000 fewer than before last week's referendum.
It reduced estimates for 2017 and 2018 by about 1.25 and 1.38 million respectively.
For 2017, global growth of auto sales is expected to 91.06 million and by 2018, it could reach 93.12 million. Previously, the forecast for 2018 stood at 94.5 million in sales.
IHS Automotive principal analyst Ian Fletcher said: The UK is, unsurprisingly, anticipated to bear the brunt of the impact.
"We currently expect that while the market will remain up in the full year of 2016, helped along by a steady growth performance during the first five months of year, despite a strong string of gains over the past few years."
One of the major issues highlighted by the forecast is about imported vehicles. The impact of UK's exit from EU can result in Great Britain Pound's depreciation compared to other currencies, especially Euro.
GB Pound's depreciation can have negative impact on import of vehicles. Due to this, IHS says that some OEMs are already considering the possible steps to be taken to change pricing of overseas-built vehicles to reduce the effect.
According to IHS, the UK's exit from the EU can have an impact on the development in Eurozone. It believes that growth outlook in Eurozone had weakened after UK's decision to leave the EU.
Prior to the referendum, IHS predicted an average growth rate of GDP in Eurozone to be around 1.7% in 2016, 1.8% for 2017 and 1.6% for 2018. Now, the forecast has been cut down to 1.4% in 2016, 0.9% in 2017 and 1.4% in 2018.
Increased instability and uncertainty could weigh down business investment and reduce employment. This could cut down the consumers' willingness to make big purchases. Businesses and consumers are likely to be affected from tighter credit conditions and weak asset markets.
