There are fears for Irish jobs following revelations that 60 B&Q stores in the UK and Ireland are to close.
It is not clear how many outlets here will be affected by the plans.
The DIY chain's parent company Kingfisher saw its pre-tax profits fall by €95m last year.
"We're learning it from the media … it's quite shocking," said Gerry Light from the Mandate Trade Union.
"There's no clear indication what locations they're talking about. As a result of those revelations this morning, we've written to the company demanding an immediate meeting with them to clarify some of these very important and concerning issues."