And there was worse news for Jaguar Land Rover, as the West Midlands-based luxury carmaker saw sales plunge by 15 per cent.
However, the SMMT is expecting a further year-on-year drop in March, as this time last year buyers were rushing to get their new cars registered before an increase in vehicle excise duty in April 2017.
Sales of diesel cars fell by 23.5% to 28,317 last month, reducing their share of the market to 35% from 44.5% a year ago.
"Higher taxes and clean air zones could be discouraging the use of diesel cars and driving a shift towards petrol, as some consumers remain undecided on the suitability of alternative fuels for their needs".
Environmental groups have called for restrictions on the most polluting cars entering towns and cities with the worst air quality.
Last month's decline will no doubt concern dealers and manufacturers, but broader analysis reveals that aside from February 2017 and 2016, one has to go back as far as 2004 to find a better February for new auto sales.
Mike Hawes, SMMT Chief Executive, said, "February is typically a quiet month as buyers await the March plate change so the rise in demand is welcome news".
He said that looking ahead, he is broadly expecting further softening in the March figure, given registrations in March a year ago were particularly fuelled by consumers pulling forward purchases to avoid Vehicle Excise Duty that came into effect on 1 April.
Sales of electric and hybrid vehicles also continued to climb, rising 7.2% in February.More news: Cultural powerhouse 'Coco' by Emeryville-based Pixar wins Oscar for best animation
RAC research found the vast majority of drivers buying new cars are paying significantly more following the changes.
Sales of cars to privates fell 2 per cent last month, suggesting that squeezed, uncertain consumers are still reluctant to make major purchases.
He added: 'The auto sector may take limited consolation from the fact that the February/January declines were less than the double-digit year-on-year drops seen over the previous three months [.].
What's causing the decline in new auto sales in the UK?
Alex Buttle, director of auto buying comparison website Motorway.co.uk, noted how sales of green cars, despite rising, are doing so at half the rate of petrol cars.
Petrol sales rose 14.4% in February, up from 51.5% of market share to 60.6%.
What's the most popular vehicle?
'Whilst sales for petrol and alternatively fuelled vehicles are increasing, they are not filling the gap.
The trends back predictions that 2018 will be the second consecutive year of declining new auto demand, as pressure on diesel and economic uncertainty continues to hamper sales.