Roches Stores will invest £70 million (€88 million) in a development plan which includes the extension and refurbishment of existing premises and the opening of three new stores.
The project will create 1,000 jobs over the next three years, according to the company.
Two new stores will be opened in the Republic and one in Northern Ireland. Mr Stephen Barry, chief executive of Roches Stores, said that although the locations were "pretty well finalised", he was not yet ready to disclose them.
The official opening of the newly refurbished Roches Stores outlet in Tallaght takes place tomorrow. More than £3 million has been invested in the 50,000 sq ft premises, which will be the first store in the Republic to carry the new Roches Stores brand image. Boxer Chris Eubank performs the official opening ceremony.
The new brand was unveiled in June in Northern Ireland, when Roches Stores opened its first store in that market. The Newry store cost £8 million.
As part of its development programme the company's outlets - Limerick, Henry Street, Dublin, and the Wilton store in Cork - will receive significant investment and refurbishment.
The 135,000 sq ft outlet on Patrick Street, Cork, has already been rebuilt and is the largest department store in Munster.
More than £10 million will be spent to refurbish the outlet on Henry Street, Dublin. The work begins next March and will involve upgrading the store to 120,000 sq ft from 80,000 sq ft .
About £15 million will be spent on rebuilding the Limerick store and the project is expected to create 150 jobs. The Galway outlet will be rebranded at a cost of £3 million.
The first of the new stores is expected to open in 2001. Details will be announced early next year. Mr Barry said the development plan indicated the company's confidence that it could hold its own against its Irish and UK-owned competitors. Growth in size would consolidate Roches Stores' position in the marketplace.
"Roches Stores has been a leading name in retailing for almost 100 years and it is our intention to be even more prominent going into the next century," said Mr Barry. "We are very excited about our development plans. We believe the upgrading of our stores will continue to position us as one of Ireland's leading department stores, offering existing and new customers more choice in a modern and friendly shopping environment."
Last year, Roches Stores reached an agreement with the Musgrave group which led to the Roches Stores food outlets becoming part of Musgrave's Super Valu chain of franchised stores. The link-up ended speculation that Roches' outlets might be sold to a British multiple.
Sainsbury was said to be interested in the independently-owned Roches, but that interest is understood to have waned when the Minister for the Environment decided to cap new superstores at 32,000 sq ft.
The Roches Stores group has 12 stores with a total turnover of more than £300 million. It employs more than 4,000 people.
Mr Barry said Roches Stores "is a family-owned Irish business and intends to stay that way".