Spanish giant Santander today launched a fresh assault on British High Street banking with the £612 million takeover of Bradford & Bingley's deposits and branch network.

Santander, which already owns Abbey and Alliance & Leicester, lined up to take on the big four of Royal Bank of Scotland, HSBC, Barclays and Lloyds TSB, which plans to merge with Halifax owner HBOS.

It took the Spaniards' share of the UK savings market up to 10% as they took on 197 B&B branches, 2.7 million new customers, and £20 billion of deposits.

The emergency deal was struck after the rest of B&B — its £50 billion of mortgages and loans — was nationalised by the Government.

The combination of Abbey, A&L and B&B gives Santander 1286 branches in the UK, 24 million customers and savings worth £116 billion.

"It really puts us in a position to challenge the big four," said an Abbey spokesman.

It was unclear how many of B&B's 2500 staff will be transferred but analysts warned job losses were likely.

Antonio Horta-Osorio, chief executive of Abbey, said: "This is good news for B&B's savings customers. They can be certain their hard-earned ­savings are with a bank they can trust as Abbey is part of the Santander Group, one of the world's most successful banks.

"The transfer of deposits and the branch network further increases the scale of our operations in the UK to around 10% of the market, an important strategic objective for us. We will significantly increase the potential of our distribution capability."

Lloyds TSB catapulted itself to No 1 retail bank with the proposed £12.2 billion takeover of HBOS. The combined company will have 38 million customers with savings of £204 billion.

Andrew Turnbull of ODL Securities said: "This is an exciting move from Santander, who have managed to weather the storm over the last year and have maintain an excellent credit status."