General Mills has been forced to pull an advertisement for Mexican food brand Old El Paso in the UK for misleading consumers.

The UK's Advertising Standards Authority said the ad had not made it clear to consumers that they needed to buy extra ingredients when they purchased the Old El Paso Crispy Chicken Fajita dinner kit.

The ASA said there had been complaints that the ad did not specify which of the ingredients - chicken, lettuce, salsa and sour cream - were supplied with the product.

In the watchdog's ruling, issued today (7 September), there were particular concerns over consumers being misled on whether chicken and sour cream were included. "Although Old El Paso Fajita dinner kits were non-chilled products, we did not consider it inconceivable for viewers to believe this was a chilled product and therefore expect chicken and sour cream to be included," it said.

According to the ASA, General Mills said it believed consumers would understand that they would need to add fresh ingredients to an ambient product. The watchdog said General Mills pointed to the fact that the ad had first been broadcast in 2008 without any complaint.

When the ad secured approval from Clearcast three years ago, General Mills added text on-screen that stated: 'Fresh chicken not included'.

However, in its ruling, the ASA said Clearcast "now understood that the kit did not come with sour cream".

The ASA added: "Although [Clearcast] understood why General Mills felt it was a fresh item that would not be expected to be supplied in the box, viewers might believe that the sour cream would come with the kit. They suggested adding on-screen text stating 'serving suggestion' to make clear that not all the ingredients shown were included in the kit."

However, the ASA said Clearcast's suggestion "would not go far enough" in explaining to viewers which ingredients were included in the kit.

The ASA said the on-screen text that stated that fresh chicken was not included was "not sufficient to remove the overall impression that chicken was supplied" and could have been overlooked by some consumers.

The voiceover on the ad, which used the term 'crispy crunchy chicken' also gave consumers "the misleading impression" that chicken was included, the ASA said. "This impression was likely to be compounded by the fact that the product was called Old El Paso Crispy Chicken Fajita," the watchdog explained.

"The ad must not be broadcast again in its current form. We told General Mills to ensure that future ads make clear that additional ingredients are also required to produce the fajita as shown in the ad," the ASA said.