Tottenham Hotspur have been warned by the Advertising Standards Authority (ASA) for an advert claiming their new stadium would be "the only place to watch the Champions League in London".
The watchdog have sent Tottenham an advice notice, warning them to "avoid making claims in future advertising that they cannot fulfil".
The north London club had hoped to have moved into their new stadium in September, but due to unforeseen delays that has been pushed back until the new year, with no official opening date in place.
They face an uphill battle in their Champions League group to qualify for the knockout round after a disappointing start to the campaign.
It is now very unlikely that Tottenham fans will be able to watch their side play Champions League football in their new stadium this season, while qualification for next year's competition is far from guaranteed.
The advertising watchdog issued Tottenham with a warning and ordered them to take down any of the adverts still appearing following two complaints it received in late October.
"The complainants challenged whether the ad was misleading because the building work of the new stadium has not been completed," an ASA spokesperson said. "Therefore it is unlikely customers will get a chance to watch Tottenham play in the Champions League at the new stadium.
"While we considered there were potential problems under our advertising rules we did not consider the issues raised were so significant as to warrant a full formal investigation. This case was assessed and dealt with via an advice notice.
"In this instance, we contacted Tottenham Hotspur and advised them to avoid making claims in future advertising that they cannot fulfil; to avoid disappointing customers. We also advised them that if the ad is still appearing to ensure it is removed. "
Tottenham released an advert in the summer claiming to be the only place in London to watch the Champions League, with digital billboards spread throughout the city and London Underground.
It also said: "Time is running out to secure premium seats at Spurs' new stadium."
After a delay in opening the new stadium, the club announced in September that they would play all their group stage games at Wembley. Their approaching match against Inter Milan may be their last in the competition for this season.
Tottenham have so far declined to comment.