Top British athletes are threatening to sue the British Olympic Association over sponsorship regulations.
Mo Farah, Katarina Johnson-Thompson, Laura Muir and Adam Gemili are among those listed as claimants in a legal letter sent to the body.
Athletes competing in the Olympics are currently bound by the International Olympic Committee (IOC) 'Rule 40'.
It protects the exclusive rights of official Games partners but prevents athletes promoting their own sponsors.
Athletes argue it unfairly prevents competitors from cashing in on the biggest moment of their sporting careers, and reduces earning potential.
Gemili, who competes in the men's 100m and 200m, told BBC Sport "a change needs to happen".
"It's ridiculous, unjust and unfair," he said.
"For us it's about creating the opportunity for every single athlete to go out there and create their own marketing opportunities so they don't have to work a full-time job."
Eilish McColgan, Martyn Rooney, Lynsey Sharp and Laura Weightman are among other British athletes listed as claimants by Brandsmiths, the legal firm behind the potential litigation.
In a statement, the BOA said because it was not publicly funded like some other federations, Rule 40 "is the protection that allows us to fund" teams for Olympics and "for all athletes".
"We acknowledge the statement made by a number of athletes today and will continue our ongoing dialogue with our Athletes' Commission and the wider athlete community in relation to this important matter," it added.
Earlier this year, the IOC softened its stance on sponsorship restrictions athletes are subject to after a ruling by Germany's competition regulator that they were too strict.
National Olympic Committees are now free to implement the updated regulations as they see fit.
Last month, the United States Olympic and Paralympic Committee was one of several that relaxed its rules, allowing athletes to thank personal sponsors and receive congratulatory messages from them during the Games.
Personal sponsors were also allowed to engage in generic advertising.
The BOA - the organisation behind Team GB - said it was reviewing its rules, and announced what it called "a new, more flexible application".
However, athletes are still not allowed to promote their own sponsors during the 'Games Period' (defined by the BOA as lasting from mid-July to mid-August 2020) and have to apply for consent for marketing activities several months before the event begins.
Gemili, who sits on the BOA's Athletes' Commission, signed the letter, which was delivered to the BOA on Friday.
Describing the changes as "disappointing", he added: "We thought there would be more change and there wasn't.
"That's why we're now taking legal action because it's not enough and there won't be any more changes from the conversations we've had, it will just be brushed under the carpet.
"It's not good enough leading into the biggest event of all these athletes' careers. We're sticking with it and we're publicly coming out and saying what needs to change, and the BOA has to listen to that."
'Is anything going to change?'
At present 12 major international brands are registered as IOC official, global partners as well as separate Tokyo 2020 sponsors and partners.
Firms pay handsomely to use trademarked Olympic phrases and imagery, with the bulk of the money recuperated for those rights being used to run the Games.
However, Gemili feels that the current rules remain to the detriment of those competing in the Olympics, particularly given the timescales involved.
"The rules put in place by the BOA mean that many athletes cannot afford to train and ultimately compete. I can't see how that's OK," he added.
"Rule 40 is very restrictive in and around the Olympic time. You can't really put anything on social media, you can't really work with brands and marketing campaigns.
"If you are going to work with anyone it has to be subject to approval by the BOA. It has to be submitted by May and a lot of the athletes won't even know if they are going to the Olympics until June.
"The BOA generates a huge amount of money. We are not asking to be paid to go to the Olympics, we aren't even asking for prize money, which many other countries provide. We are just asking for a bit of flexibility to go out and create our own sponsorship opportunities around the biggest moment in our careers.
"Working full-time applies to 99% of athletes and they don't have the voice or the platform to come out and speak against the BOA and against Rule 40 because they are scared of what might happen.
"I'm lucky enough and I'm on the board of the BOA Athletes' Commission and I've had a lot of messages from a lot of different athletes asking, 'Is anything going to change? Can you speak to them?' That's why I thought it was necessary to put my face on this and say, 'Yes, things need to change'."
Adam Morallee, the lawyer acting for the athletes, told BBC Sport: "The German decision is not binding on the English courts, but the case is clearly a very strong one and we fully expect a similar result.
"The athletes simply want parity with Germany, and an opportunity to participate in sponsorship revenue driven by the Olympics."