The wholesaler said the increase, which follows a hike of 4.8% last year and will come into effect on 7 August, was due to "the sharp rise in transport and fuel costs".
"We are always mindful of the impact on our customers and have limited the charges accordingly," insisted CEO Mark Cashmore, who added that the average increase for customers would be 3.33%.
However, the National Federation of Retail Newsagents said it was "absolutely appalled".
"This action epitomises the unacceptable face of monopoly when a wholesaler uses its absolute power to force retail customers to pay for its own rising costs," said national president Kieran McDonnell.
"It is about time we had some serious discussions about an alternative way of funding wholesalers."