Santander has pulled out of talks with Royal Bank of Scotland to buy more than 300 Williams & Glyn branches, according to the Financial Times.
The talks fell through due to RBS asking for more money than Santander were willing to pay.
Interested bidders are BBVA, Secure Trust and Virgin. The network has been valued at around £2bn.
RBS must sell Williams & Glyn by the end of next year, according to the terms of its state bailout.
Santander made a formal offer for the network earlier in the year.
The RBS branches will be rebranded as Williams & Glyn after a sale, creating the UK’s seventh-largest retail bank.
The network would have 1.7 million customers and 2 per cent of the current account market.
Santander first tried to buy Williams & Glyn in 2012.
In April, RBS said it doubted it would sell the network by the end of 2017.
It said that building a separate IT platform for the sell-off is “challenging” and it is trying to find other ways to separate and sell Williams & Glyn.