Travel firm MyTravel has said job losses are "inevitable" as a result of its planned merger with Thomas Cook.
MyTravel shareholders need to approve the deal
But the firm said it was "too early" to give specifics, saying the situation would become clearer within the next six to eight weeks.
The Transport & General Workers Union (T&G) has expressed fears that a merger with Thomas Cook, owned by Germany's KarstadtQuelle, would cause job cuts.
MyTravel, the name behind Going Places and Airtours, employs 15,000 people.
A MyTravel spokesman said "job losses are inevitable when two firms merge in this industry".
However, he added that MyTravel had always sought to "redeploy" workers after job losses wherever possible.
This was the case when the firm closed a number of Going Places outlets in the past 18 months, he stressed.
The merger - which has yet to be approved by MyTravel shareholders and the competition authorities - is expected to be finalised by June.
KarstadtQuelle would own 52% of the combined firm while MyTravel would own the remainder.