Barclays is set to acquire ING Direct UK, taking on the latter's £10.9 billion in deposits and £5.6 billion mortgage book.
The Dutch banking group announced its plan to conclude its UK operations in August 2012, as it looks to raise funds to repay a bailout from the Netherlands government in 2008.
Its deal with Barclays will involve transferring some 750 ING employees and 1.5 million customers over to the London-headquartered institution.
Boss of Barclays UK retail banking Ashock Vaswani commented: "We intend to maintain the high standard of service and honour the existing terms and conditions [customers] have experienced with ING Direct."
ING said it would incur a €260 million (£210 million) loss after tax on the sale, which is partly due to its agreement to auction its mortgages to the bank at a price of three per cent below the level ING values them in its accounts.
At 09:50 BST, Barclays was down 0.1 per cent on the London Stock Exchange to 22.05p per share.
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