Unilever UK plans to do for laundry detergents what has already been done for fabric softeners with the launch of concentrated versions of two of its biggest brands.

It is investing £15m in Small & Mighty, which will be launched simultaneously under the Persil and Surf brands. The 750ml bottle features a measured cap to ensure the correct 35ml dosage per wash is used.

Like the existing 1.5 litre diluted liquid format, the new half-sized variant provides 20 washes per bottle.

Unilever hopes the new lines will add value to the sluggish laundry category.

"Small & Mighty is an excellent example of how we can bring direct benefits to the consumer and to the retailer," said Persil brand manager Zoe Hayward.

"We expect consumers to trade up from their current 'dilute' liquid."

The concentrate is significantly smaller than other liquid products, which makes it easier to carry and store, she added. It also offered greater supply chain efficiency as it allowed for 156% more SKUs per ­pallet.

Unilever originally launched Small & Mighty in the US, where it pioneered the move into concentrated liquid formats.

Persil Small & Mighty will be available in the UK in five variants: biological; non-bio; colour; aloe vera; and with freshness of Comfort- all at the premium price point of £3.69. Surf Small & Mighty is available in Surf Sunshine and Surf Tropical, priced at £2.89.

Unilever said it would only keep three core Persil dilute variants from its existing liquid range while others, and Surf variants, would be replaced by Small & Mighty.

The company said the product, which appears in stores this month, would offer environmental ­savings through the use of 41% less plastic resin, 43% less carton usage and a 60% reduction in water usage.

It also estimated a 60% reduction in the number of cases that would need to be transported.

The £15m investment will include TV, press and poster advertising, as well as an online and sampling campaign.