News International has been accused of threatening to stop supplies to an independent news retailer who has added a surcharge to the price of the weekend Sun.

Since February, when News International cut the price of its Saturday paper to 50p and launched the Sun on Sunday, also priced at 50p, Walter Bush of Baginton Village Stores near Coventry has added a 10p surcharge to both newspapers to ensure his margin is maintained.

But despite a Trading Standards official approving his action, News International told Walter that his supplies of The Sun would be stopped if he persisted with the higher price, according to the National Federation of Retail Newsagents (NFRN).

NFRN president Alan Smith said: “By bullying one individual newsagent by threatening to stop his supplies when the action he is taking is both fair and legal shows that NI, and by association Rupert Murdoch, have finally lost their marbles.

“When publishers attack our margins there are two obvious ways that members can fight back – they can disregard the cover price or give preference to those titles that provide a more viable margin.

“The printed cover price is only a recommended retail price so Mr Bush, and any retailer who wants to, can surcharge the title to make sure the profit they want to make from the newspaper is maintained.”

Julian Davies, director of partner sales, News International, said: “News International will be following up with the retailer to resolve this situation.”