TUI Travel has announced plans to close 100 of its 1,100 UK Thomson and Firstchoice travel agencies, plus cabin crew at thomsonfly are also in the firing line.
The shop closures, due to the merger of TUI with First Choice, will focus on branches which are unprofitable or in locations where there is more than one shop.
The group has also begun redundancy consultations with staff at its offices in Crawley and Manchester, which are due to close and relocate to Luton.
TUI said it hoped most of the losses would be through staff turnover.
The announcement of shop closures has heightened the concerns of staff at Thomsonfly, whose union, Unite, has already been in discussions with TUI.
Unite has asked 1,700 cabin crew at Thomsonfly if they will support a full strike ballot after TUI failed to guarantee there would be no compulsory redundancies.
The vote is due to take place tomorrow (Wednesday).
A spokesman for Unite said: “With the redundancies announced by TUI today, cabin crew are even more concerned.
“It is complicated because Thomsonfly staff are not yet employed by TUI Travel.”
If there is a majority vote in favour, the union will have 28 days in which to take strike action and is required to give seven days notice of what action will be taken.