As of 1 October the merged firms will work under the Mason Hayes+Curran brand and name.

The combined firm will employ around 270 staff, with its newly-merged headquarters in Dublin. Mason Hayes is the only Irish firm to reveal its financial results and this year recorded a 14% hike in turnover to just over E32m (?25.7m).

The firm has offices in London and New York and has strengthened in corporate and financial services in recent years.

Arthur O'Hagan, one of the longest established law firms in Ireland having been founded 150 years ago, has a strong reputation in the healthcare, education and charity sectors.

Mason Hayes managing partner Emer Gilvarry said: "The merger will deliver significant benefits to clients of Mason Hayes and Arthur O'Hagan and will broaden the legal expertise and services available to the clients of both firms. Arthur O'Hagan has an excellent reputation and market-leading expertise across a number of practice areas which we look forward to bringing to our client base."

John Gleeson, managing partner of Arthur O'Hagan, added: "Arthur O'Hagan has adapted its business and services to the evolving needs of its clients over many years. The merger is the most natural progression of this approach and it is a positive development for our clients and staff."