Coca-Cola Enterprises is ­re'vamp'ing its Relentless range in a gothic style akin to the merchandising for the Twilight movies.

The soft drinks giant is introducing the design this month and is adding a fifth variant to the range. Relentless Libertus is a sugar-free version of the drink, but with the same flavour as the Origin line.

The launch will be supported by a multimillion-pound marketing campaign later this year.

"Libertus will increase shoppers' choice in diet ­energy," said Stuart Agates, head of energy.