Thomson tour holiday operator TUI Travel is undergoing a two-year restructuring process after a merger of TUI's travel division and First Choice.
The company has not said which of its 1,100 UK stores will be closed or how many jobs are expected to be lost.
advertisementTUI will keep the two travel agent brands, Thomson and First Choice, separate.
There are currently Thomson shops in Friargate, Preston and Hough Lane, Leyland.
There are three First Choice shops in Preston - at Friargate, Deepdale Park and Fulwood ASDA.
A TUI spokesman said: "TUI Travel UK is continually evaluating the performance of its retail outlets.
"This is usual business practice for any retailer and continues throughout the integration.
"TUI Travel UK is not expecting large-scale shop closures.
"In total, it is estimated that up to 100 retail units will close by the second year of the integration.
"Where there may be a proposal to close a unit, TUI Travel UK will liaise closely with team members to find opportunities for re-deployment."
The spokesman said that job losses were not an inevitable part of the shop closures.
The merger between First Choice and German-owned TUI in March last year created Europe's biggest travel group with 48,000 staff and 27 million customers.
The cuts follow a 100-day review led by chief executive Peter Long, who previously ran the First Choice business.
TUI said at the time of the merger that it was committed to building up internet sales and saving £100 million a year through costs and streamlining its retail shop operation.
This figure was increased to £150 million a year, with £40 million of the increase relating to the UK.
The company said further cost savings had been identified in its airline network as well as in general administrative costs, although it did not give...