Irish bookmaker BoyleSports has said it is concerned at the decision by Ladbrokes and Gala Coral to sell 359 of their shops to existing UK retail competitors.
In a statement, the bookie chain said it was disappointed at the decision and would communicate its concerns to the Competition and Markets Authority.
It also said it would review its options on what other steps may be open to it.
In a statement, BoyleSports said that its bid for the shops was higher than the reported sale price, was fully-funded and was cognisant of the changing political and regulatory UK landscape.
It could also have been completed within two weeks of acceptance, it added.
"BoyleSports believes the decision not to allow a challenger brand onto the UK high street is bad for retail consumers who would have benefited from the keen pricing and excellent service already available to our existing Irish retail customers and to online customers in Ireland and the UK," the company added.
It emerged earlier today that Ladbrokes and Gala Coral had agreed to sell 359 shops for £55.5m to UK-based rivals.
The sale deal would will reduce their footprint in the UK and pave the way for competition authorities to allow their merger to proceed.
The pair were told in July they must sell around 350 to 400 shops in order to obtain clearance for their proposed merger.
Ladbrokes agreed the terms of a £2.3 billion all-share merger with Coral in July 2015, and shareholders backed the deal in November.
Under the shop sale deal, which is conditional upon completion of the merger, rival bookmaker Betfred will buy 322 shops for £55m, while Stan James will purchase 37 shops for £500,000.
