The rival manufacturer Dyson challenged the claims that the cleaner was designed to last up to 20 years and that it had been designed and tested for 20 years' average use.
It also objected to a further claim that the company subjected the cleaner’s motor to a lifetime test of 1,000 hours – 400 hours beyond that which international test institutes demand.
Miele defended its test programmes, explaining that they were designed to simulate strain on the product based on average household use.
The company said it estimated annual use based on consumer research, which indicated that most respondents vacuumed one hour a week.
It said that this equated to approximately 1,000 hours over a 20-year period.
Miele believed most products would last for 20 years but argued the ads’ claims were not absolute as there may be some cases where the 20-year lifespan was not reached.
The Advertising Standards Authority said that consumers would interpret the claims to mean it was very likely that the product would still be working in 20 years' time.
Due to the fact it was not possible to determine the longevity of the product when used by the consumer, the regulator concluded there was not sufficient evidence to support the claims.
It also noted from test data provided by Miele, the S7 motor would not always last 1,000 hours and therefore concluded both ads were misleading.
The ads, by the agency Poulters, must not be shown again in their current format.