Susie Verrico, 43, hoped her life would be changed by the contest

The watchdog said Nestle and Channel 4 should have been clearer on terms and conditions on marketing material for the contest on KitKat bars this summer.

Earlier it warned the organisers for failing to use an independent observer when model Susie Verrico was picked.

Nestle said it did not mean to mislead and promised to learn from the ruling.

The search for an extra contestant on the popular reality show saw 100 special tickets hidden inside KitKat chocolate bars.

We told Nestle to ensure any future campaigns included all significant conditions of entry to avoid misleading and disappointing consumers Advertising Standards Authority statement

But some adverts promoting the "golden tickets" failed to mention that entrants had to be aged 18 or above, while a poster failed to include the competition closing date.

These were breaches of advertising rules relating to truthfulness and sales promotions which could "affect a consumer's decision to enter", the authority said.

"We told Nestle to ensure any future campaigns included all significant conditions of entry to avoid misleading and disappointing consumers and advised them to seek guidance from the Committee of Advertising Practice copy advice team before advertising future prize promotions," the watchdog said.

Nestle insisted all of its other marketing material "referred consumers to the Channel 4 website, where full terms and conditions could be found".

It was never our intention to mislead consumers as to the promotion's terms and conditions Nestle statement

It would study the ruling "very carefully and ensure that learnings are applied to future advertisements", it said, adding that the promotion in question was no longer being used.

There is still one outstanding issue regarding the seventh series of Big Brother which is being investigated by Icstis, the premium rate watchdog.

It has yet to decide whether its code was breached when viewers were invited to reinstate an evicted contestant.