The Royal Bank of Scotland (RBS) is to start charging some of its top corporate clients to hold cash with the bank.
RBS wrote to some of its largest investment banking customers this week to tell them it could no longer let them keep cash held as collateral in their accounts for free and will impose negative interest rates from next week.
Read more: RBS to ditch "RBS" brand
In the letter, RBS, which is still 73 per cent owned by the state, said: "As you will be aware there are a number of currencies which now attract negative overnight rates for deposits.
"To date we have been flooring deposit rates at zero per cent, but we have now reached the stage where we can no longer sustain this level of floor.
"As a result of the continuing interest rate situation we will be implementing negative interest rates."
The move will apply to a very small number of big corporate clients, around 60, that trade futures and options contracts in sterling and euros and are required to post collateral in cash with RBS as part of their trading. The new negative rates will come into force on Monday.
Regular personal and business accounts at RBS will be unaffected by the switch.
A number of high street lenders, including Santander and Nationwide have cut the interest rates they offer on savings and current accounts in response to the Bank of England's decision to slash interest rates to 0.25 per cent.
Banks have come under pressure in the low-interest rate environment as sub-zero rates place excessive pressure on their net lending margins and eat into profits. The UK's vote to leave the EU in June exacerbated this pressure by raising the prospect of rates in the UK being stuck at extraordinary lows until the end of the decade.
Laith Khalaf, senior analyst at Hargreaves Lansdown said: "We are venturing through the looking glass when it comes to interest rates, where individuals and institutions are basically being pushed up the risk spectrum by central banks.
"We are still a long way from banks imposing negative interest rates on personal customers, which would be a deeply unpopular move, though clearly the direction of travel is concerning for savers."