The move follows the recent announcement by the Secretary of State for Business Peter Mandelson that wholesalers would no longer be bound by the National Newspaper Code of Practice, a recommendation made in a recent Office of Fair Trading (OFT) investigation.
Retailers in rural locations, and those who sell small quantities, were concerned that wholesalers would decide they were uneconomical to supply.
Smiths News chief executive Mark Cashmore said: "We want to reassure the industry and have therefore given a guarantee to continue supplying all existing customers, regardless of their size or location."
Smiths said it would notify retailers shortly about any change in carriage service charges.
The wholesaler also announced that it would take a positive view of sub-retailing and would not be applying minimum entry levels (MELs) to new retailers. "We agree with the OFT's recommendation that MELs are no longer appropriate," said Cashmore.