New-plate car sales in Wales last month slipped 3.41% to 15,783.
That was the average for the UK as a whole but in Scotland it fell almost 10% and the total UK registrations in March reached 457,220.
In Wales, the top ten was dominated by Ford with Fiesta, Kuga and Focus taking the first three places, followed by Yaris, Corsa, Qashqai, Polo, Golf, Sandero and Ecosport.
It was the only part of the UK where Ford took the top three places, reflecting the existence of the Ford Bridgend Engine Plant and multitude of Ford dealerships.
Political and economic uncertainty and continuing confusion over diesel affected demand, according to the Society of Motor Manufacturers and Traders.
March is a crucial month for the new car market, as the plate change drives buyers into showrooms, with new car demand often seen as a bellwether for consumer confidence and the health of the wider economy.
Demand fell in both the private and business sectors, with registrations down -2.8% and -44.8% respectively, while fleet demand was stable, up 0.3%.
Declines were seen across almost every vehicle segment, including popular Dual Purpose (-1.8%) and small family cars (-4.0%). However, superminis – Britain’s favourite vehicle type – saw a 4.3% increase in demand, taking a third (33.7%) of all registrations.
Following the trend of recent months, diesel registrations fell -21.4% while petrol demand grew 5.1%. Meanwhile, demand for Alternatively Fuelled Vehicles (AFVs) increased by 7.6% with 25,302 registered, the biggest March volume on record.
With almost 40 plug-in models on the market in the UK, and over 20 more expected to arrive in 2019, demand for these new technologies is expected to continue to grow.