The banking group said it can now compete with the lenders already established in Britain as it revealed its earnings during the period were greater than those achieved in the previous quarter and the correlating three-month period in 2010.
It added that - over the last 15 months - its UK liquid asset holdings have swelled by Â£30 billion ($49.9 billion).
Ana Botin, chief executive at the institute, said: "Santander UK has established solid foundations and we are already proving a strong challenger for the incumbent banks."
She added the firm has maintained a competitive range of products for its retail, business and corporate customers.
Barclays, one of the largest banks in the UK, recently announced a fall in first-quarter earnings following a weak investment banking performance.
By Gary Cooper