BMW and its Mini offshoot have caved in to demands to let dealers put their cars on a price comparison site.
The U-turn comes as the competition regulator was threatening an inquiry.
The pressure is being seen as a clear signal to firms that they must not stop the public taking advantage of the power of the internet to find bargains.
BMW had put a ban on its dealers using Carwow, which connects car sellers across the country with buyers hunting for the best price.
The website appealed to the UK’s Competition and Markets Authority (CMA), accusing BMW of putting a road block in the way of legal competition.
‘Time is right’
Carwow argued that dealers with cars at competitive prices were clamouring to be given permission to use the site and speed up their sales.
After months of wrangling, BMW reversed its original decision, as it became clear that the CMA was on the brink of launching a formal investigation.
Car sales – new and old – are moving increasingly online, with other websites, such as Webuyanycar, Tootle and Wizzle, also making inroads.
James Hind, Carwow’s founder, said: “It shows this is a consumer trend which is not going to abate.”
He believes 90% of car buyers do their research online, though even Carwow’s users then complete their purchase direct with the dealer.
The CMA has made no secret of its enthusiasm for promoting the potential of price comparison sites to strengthen the hand of consumers.
A spokesman for BMW said: “The time is now right to enable our UK retailers to explore the additional sales opportunities that are becoming available through internet-based new car portals.
“Over the coming months we will be working with our retailers and learning from their experience to ensure we continue to provide a consistent premium buying experience for those customers who choose to purchase a BMW or Mini product through these new channels.”