The Facebook ad also claimed it was a 'clinically-tested alternative to birth control methods'
An advert purporting that a contraceptive app was "highly accurate" has been banned by the UK's Advertising Standards Authority.
Natural Cycles, a smartphone app which claims to offer an alternative digital birth control, was warned "not to exaggerate" its efficacy after its Facebook ad claimed it "provided a clinically tested alternative to other birth control methods".
The UK watchdog found the claims to be misleading after it received five complaints.
The advert said: "Natural Cycles is a highly accurate, certified, contraceptive app that adapts to every woman's menstrual cycle.
"Sign up to get to know your body and prevent pregnancies naturally."
The watchdog said that the Facebook ad must not appear again in its current form.
In its ruling, the ASA said: "In the context of the ad, the claim 'highly accurate contraceptive app' would be understood by customers to mean that the app had a high degree of accuracy and was therefore very reliable in being able to prevent unwanted pregnancies.
"We further considered that the claim 'clinically tested alternative to birth control methods', presented alongside the 'highly accurate' claim would be understood to mean that the app was a reliable method of contraception which could be used in place of other established birth control methods, including those that were highly reliable in preventing unwanted pregnancies."
Natural Cycles, founded in Sweden by nuclear physicist Elina Berglund Scherwitzl and her husband, tracks ovulation day, cycle length and the average temperatures of different phases throughout the menstrual cycle.
Women are required to take their temperatures every day using a basal body thermometer and enter the reading into the app.
Since its launch in 2017, the app has more than 300,000 users who pay a monthly or annual fee for the service, but the company has been embroiled in controversy after 37 women reportedly fell pregnant whilst using the app.
However, it has become the first contraceptive smartphone app to be officially approved in the US.
The US Food and Drug Administration described the app as an effective method of contraception if "used carefully and correctly".
Natural Cycles was contacted by The Independent for comment.