Great Britain's Olympic hopefuls could end up in hot water with the Office of Fair Trading, who are attempting to crack down on 'deceptive' advertising on Twitter.
Tom Daley and Rebecca Adlington are amongst the stars who have been tweeting about cars when they have a sponsorship deal in place with the manufacturers.
And athletes gunning for gold in this summer's Olympics are talking about everything from nail varnish to cereal on the social networking site.
The Office of Fair Trading have warned that "online advertising and marketing practices that do not disclose they include paid for promotions are deceptive under trading laws."
Synchronised swimmer Jenna Randall states in her profile the names of her five main sponsors, but a number of her fellow Olympic prospects do not.
For instance diver Tom Daley, who is sponsored by Mini, posted a picture hailing his parking in the car, but his profile makes no mention of his link with the brand.
Several BMW-sponsored stars, including Adlington, have also spoken on Twitter of their delight with the cars.
The German manufacturer, who are the Automotive Partner of the Olympic Games, were reported in the Daily Mail stating their athletes are "not contractually obliged" to promote their cars on Twitter, but are "pleased" that they are enjoying them.
The Office of Fair Trading are keen to clarify the rules of advertising on Twitter, which were tested when several celebrities including Katie Price and Rio Ferdinand were paid to promote Snickers with some out-of-character tweets.
Athletes, meanwhile, are keen to make the most of their earning potential, with the Olympic Games in their home country a unique chance to be in the public eye.
"We are almost talking about setting certain athletes up for life," said Gab Stone, agent to Olympic gymnast Louis Smith.