Customers who hold money with Northern Rock and Virgin Money have received reassurance that they would still be entitled to the same levels of compensation if the institutions went under.
The Financial Services Compensation Scheme (FSCS), which protects money in banks, building societies and credit unions, said that both organisations will maintain separate banking licences when the sale of Northern Rock to Virgin Money goes through on January 1 next year.
This means that customers will not see their compensation limits slashed in half if the banks hit trouble and they can still claim the full amounts.
The level of deposits covered by the scheme stands at £85,000 for single accounts and £170,000 for joint accounts.
Mark Neale, chief executive of the FSCS, said: "Those people who have money with both Northern Rock and Virgin Money can be reassured that the two brands will operate under different banking licences.
"Those with large amounts of cash should remember to always try to keep within the £85,000 FSCS deposit limit, or £170,000 for joint accounts, per banking licence to protect their money. Anyone with savings above those limits should consider spreading their money around to ensure it is safe."
A spokeswoman for the scheme did not rule out the possibility of the two licences merging in the future, but she said: "For now they are two separate licences."
The sale of Northern Rock to Sir Richard Branson's Virgin Money was announced on Thursday, in a move which could shake up the banking industry but leaves taxpayers with a potential £400 million loss.
Around £14 billion of mortgages and £16 billion of savings are held with Northern Rock, which was nationalised in 2008 following its near collapse. Customers will be able to continue operating their accounts as they do now.
Virgin currently offers products including credit cards, savings and investments and general insurance.