Natwest has become the first bank to warn business customers it may charge them negative interest rates on money held in current accounts.

In what is believed to be a UK first, the bank has signalled its intention to force account holders to either pay to hold money or move funds elsewhere.

Although current plans for negative rates are restricted to business customers, fears are mounting that "pay to save" rates could soon become a reality for millions of consumers, if other banks follow suit.

The outgoing pensions minister, Ros Altmann, warned negative interest rates on current and savings accounts pose a threat to the financial security of older savers, who often rely on their savings to provide a retirement income.