Primark is moving 220 of its English-based jobs to Dublin.
From September, the brand - which operates here as Penneys - will merge a number of departments here.
Primark will amalgamate all of its buying, merchandising, design, quality and sourcing operations in Dublin.
220 staff in Reading will be given the option to move to Primark's headquarters on Mary Street.
Primark has denied the decision had been prompted by Brexit.
Paul Marchant, CEO Primark said:
"Currently, our product operations are separated across two locations, Dublin and Reading".
He explained the merger will "ensure our business strategy and our expansion into new international markets is fully supported.”
Lorraine Culligan, Group Director People & Culture Primark, said "All of our people who are in any affected roles will have the opportunity to work in Dublin".
