The owner of the Slug & Lettuce and Be At One chains is being investigated over concerns about possible “unfair” treatment of landlords who run more than 3,000 of its venues.

Stonegate Group, Britain’s biggest chain of bars and pubs, could be fined up to 1% of revenue, more than £16m, if it is found to have breached the “pubs code”, legislation governing how pub-owning companies treat their tenants.