An extra-strong Marmite designed for "hardcore Marmite lovers" is set to hit shelves next year, and fans of the spread are being asked for feedback on the final flavour through a social media campaign.

Marketing behind the launch of the extra-matured version of Marmite set to hit shelves next year kicked off this week with fans of the spread being invited to join a new social media group called Marmarati. Brand owner Unilever described Marmarati as a "quirky, Victorian-style secret society for Marmite eaters".

Members will be the first consumers to sample the spread and will be asked for feedback on the flavour, which Unilever claims will affect the final recipe.

"With thousands of Marmite fans regularly talking about Marmite online, we felt it only right to get them involved in the launch," said marketing manager Tom Denyard.