Mars, which has pledged to limit its products to a maximum of 250 calories per portion by the end of next year, is to roll out a limited-edition Mars bar weighing in at just over 200 calories.

Available in stores from 10 September, Mars Caramel is similar to a regular Mars bar – but with the nougat layer removed. The 45g bars contain 204 calories compared with 260 calories in a 58g Mars bar.

The company said the product had already enjoyed success in the US, Canada and Australia, and would tap into growing consumer preference for caramel - now one of the top three flavours  in the chocolate category.

As part of its Responsibility Deal Pledge, Mars has promised to limit products to a maximum of 250 calories a portion by the end of 2013. In June, Mars UK MD Fiona Dawson said reformulation might not be enough to hit the target and that some bars would have to shrink.

“We’re looking at the options and experimenting with a number of different sizes with customer groups,” said Dawson.

Although Mars had cut 15% of the sat fat content from Mars Bars in 2010, there was “only so much reformulation you can do”, she added.

If a regular Mars bar was reduced to the 45g weight of the new Mars Caramel, its calorie count would drop to 202.