Yesterday, free paper Metro ran a wraparound cover advert for its low-carbon motor festival ecovelocity in London featuring a Stig-like figure dressed in a white racing suit and helmet.
The mysterious figure was adorned with flowers to denote the event's "green" credentials, and was referred to only as "Clive". The text added that "some say he once rode to Norway on a seal", similar to the introductions on Top Gear before The Stig appears.
In a statement issued to The Guardian, a BBC Worldwide spokesman said: "We were surprised to see the creative that Metro have chosen to promote this event and would like to make it clear that it is not associated with either Top Gear or the Stig character in any way. We are currently assessing our options regards next steps."
Metro's promotion also comes at a time when BBC Worldwide is preparing to promote its own Top Gear live motoring event, also held in London.
Top Gear's "tame racing driver" The Stig has become a valuable asset for the BBC, and producers have gone to great lengths to hide the character's real identity.
Last year, the BBC unsuccessfully attempted to block the publication of an autobiography by racing driver Ben Collins discussing his time as The Stig.
At the time, Top Gear producer Andy Wilman said in a blog post that The Stig, like Doctor Who's Tardis, "belongs to the licence payer, and not to some opportunists who think they can come along and take a slice when they feel like it".