If put into place, it would make them the first UK banks to introduce negative interest rates. Only business customers are affected.
The banks have written to 1.3 million business and commercial banking customers to warn that the group may charge customers for their deposits if the base rate slips below zero.
The last Monetary Policy Committee meeting saw the base rate held at 0.5% despite strong predictions that a cut to the interest rate would be made.
The letter said:
"Global interest rates remain at very low levels and in some markets are currently negative. Dependent on future market conditions, this could result in us charging interest on credit balances."
