The Valleys TV ad featured young people at a house party, with scenes including a woman bouncing on the sofa so you could see her pants; women flexing their breasts; two women kissing; men and women kissing; and a woman touching a man's stomach.
Watch the advert below (warning - adult content):
The voiceover said: "The harder they party, the harder they fall. Will they make it in Cardiff, or will they just end up back in the valleys? Brand new reality, coming soon to MTV."
The ad was cleared by Clearcast, the body which approves ads for broadcast, but was given the restriction that it should not be shown in or around programmes specifically targeted at children.
However, four complainants, who had seen the ad between 8pm and 9pm during Eddie Stobart: Trucks & Trailers and The Fresh Prince of Bel-Air, said that due to the sexual content it was inappropriate to schedule the ad before the 9pm watershed.
Following an investigation, the ASA also found that the advert had been shown before 7.30pm, when children could have been watching.
After being contacted by the ASA, Clearcast said that it felt that the ad "did not go any further in terms of real or implied sexual content" than other reality TV shows, and considered an ex-kids restriction was "sufficient".
The body felt that the visuals were "of a comic, slapstick nature rather than serious sexual content".
It said that the advert's ending, which showed the couples emerging in a field full of sheep, "underlined the idea that the group were having fun away from home rather than engaging in seductive or overtly sexual behaviour".
The ASA acknowledged that the advert did not contain any explicit nudity, but noted that it did feature a number of shots that "focused on breasts" and had suggestive scenes.
"Many of the interactions between individuals at the party were depicted with a sexual element and we considered that the overall tone of the ad was sexual," the ASA added.
"We therefore considered that the ad was not suitable for broadcast when younger children might be watching. We concluded that the ad was not suitable for broadcast before 7.30pm and that the scheduling restriction applied was not sufficient."
The ASA judged that the sexually suggestive content was not sufficient to warrant a post-9pm restriction, but warned MTV that it must not appear again in its current form before 7.30pm.
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Photo gallery - The Valleys launch photo call:
Copyright: Rex Features