All staff at one branch have resigned, TTG understands, with colleagues at a further two stores also leaving. The three branches affected are Blaby, Nuneaton and Syston.
It is understood some of those who decided to leave did so over differences of opinion about how operations would continue under Hays Travel.
Guy Fletcher, Millington Travel's sales and marketing director, moved to reassure TTG it was business as usual for Millington Travel.