The Post Office, which partners with Bank of Ireland (>> Bank of Ireland) to offer banking services, said it would launch the "Post Office Money" brand which customers could access in its 11,500 outlets or online.

The move is intended to present the Post Office as a challenger to Britain's biggest banks, which have been hit by scandals ranging from the mis-selling of loan insurance to the attempted rigging of benchmark interest rates.

Lawmakers and regulators are keen for challengers to emerge to break the dominance of Britain's "Big Four" lenders, Lloyds Banking Group (>> Lloyds Banking Group PLC), Royal Bank of Scotland (>> Royal Bank of Scotland Group plc), Barclays (>> Barclays PLC) and HSBC (>> HSBC Holdings plc), which control more than three quarters of personal current accounts and make nine out of 10 loans to small businesses.

"Post Office Money is committed to providing customers with an offering that is fair, accessible and helps them manage their financial needs," said Nick Kennett, director, financial services, at Post Office Money.

Other new entrants include Metro Bank, which said last week it had increased lending by 112 percent in 2014.

The Post Office began offering personal current accounts in 2013 in an attempt to broaden its customer base. It already has 3 million customers for its banking and insurance businesses and 9 million using its foreign currency service. Post Office Money will also offer home loans, savings products and travel insurance.

Post Office Money is looking to take advantage of Britain's biggest banks closing branches, which has been criticised as leaving some consumers without easy access to a local branch.

It will offer customers extended opening hours and Sunday opening at 2,500 branches.

Separately on Monday, Spanish bank Santander (>> Banco Santander, S.A.) said it had reached an agreement with the Post Office for its British customers to bank at the Post Office's outlets.

Santander said the arrangement was part of a wider investment programme that has involved it refurbishing 40 percent of its branches and investing in technology.

(Editing by Steve Slater and David Holmes)

By Matt Scuffham