Boil in the bag ready meals will be the next big thing at the premium end of the category, Waitrose executive chef Neil Nugent has claimed, as the retailer extends its range of sous vide ready meals.

Sous vide or 'under vacuum' involves slow cooking and vacuum sealing food, which can then be reheated by immersing it in simmering water.

"I'd be surprised if there was a ready meal maker not looking at it," Nugent said

Asda has claimed its Extra Special Lamb Shanks cooked sous vide is one of its best sellers. But not all feel sous vide will be a hit.

"Do consumers want to buy foods in bags?" said Kerry Foods innnovation director David Hamilton. "Not really."