Danske Bank has secured approval from all relevant authorities for its 10.4 billion crown (€1.4 billion) acquisitions of Northern Bank and National Irish Bank.
The banks' new Danish owner said they would operate as separate entities with their own management and staff functions but will share a number of support functions.
Don Price, who has been chief executive of both operations, will be chief executive of Northern Bank. NIB's chief operating officer, Mr John Trethowan will become acting chief executive of the operations in the republic until a permanent appointment is made.
Both banks' chief executives will sit on the executive committee of the Danske Bank Group.
The Irish Bank Officials Associations (IBOA) welcomed the news that the deal had passed the regulatory hurdle. "IBOA very much welcomes Danske Bank's purchase of both banks as it ends the uncertainty about the future of the banks, which will in itself bring considerable relief to both staff and customers," said general secretary Larry Broderick.
He added: "IBOA has had a number of constructive meetings in recent weeks with Danske Bank." It has also met the union that represents bank staff in Denmark.
Danske expects the cost of integrating the two banks to amount to 1.5 billion crowns, 500 million of which it expects to spend in 2005. "The acquisition offers a solid basis for growth, and we have now started the integration process which will run until Easter 2006," Danske chief executive Peter Straarup said in a statement.
By then both banks will have access to Danske's shared IT platform, it said.
By yesterday evening, Danske shares were 0.6 per cent up at 172.50 crowns in line with the Copenhagen bourse's top-20 KFX-index.
The two banks, which Danske acquired in December last year from National Australia Bank, will continue to operate under their own brand names but will adopt the visual corporate identity of Danske Bank.
Northern Bank is market leader in Northern Ireland with a market share of around 20 per cent. National Irish Bank has a market share of around 4 per cent.
Danske sees a considerable potential in the bank and expects to open new branches, it said.