The US bank said that it planned to close its Doxford call centre near Sunderland, where 400 people are employed, and 49 CitiFinancial branches, employing 300 people. The businesses will stop offering new loans from tomorrow.
Citigroup said that it was shutting the sub-prime businesses to concentrate on its more upmarket Citi and Egg brands.
The bank is consulting with the staff affected and it is understood that some may be offered jobs elsewhere in the group.
Future Mortgages specialised in providing first and second mortgages to sub-prime borrowers applying through brokers and other intermediaries, while CitiFinancial provided unsecured loans again to borrowers introduced through intermediaries.
Bert Pijls, business manager for Citi's UK consumer business, said: "Following a strategic review of the consumer business in the UK, Future Mortgages and CitiFinancial were not identified as areas for strategic growth.
"By proposing to focus resource on our Citi and Egg brands, we are reflecting Citi's global strategy and creating a platform for expansion in the UK personal finance market."
Pijls took over in March after the departure of Ian Kerr, the previous head of the operations who left shortly after Egg wrote to 161,000 customers cancelling their cards because, it claimed, they had poor credit records.
Citigroup's move comes two weeks after used by its recently acquired Goldfish credit card business.