The Consumer Price Index rose slightly to 2.1 per cent in July – up from 2 per cent the previous month. The change means the number of savings accounts beating inflation has tumbled from 110 to just 58, according to Hargreaves Lansdown.

The investment company said savers now need to fix for at least 18 months to beat inflation in the mainstream market – its analysis excluded niche accounts such as Help to Buy, Help to Save, children’s accounts, Junior ISAs, accounts restricted to existing account holders, and those offered in very restricted areas.

Sarah Coles, personal finance analyst at Hargreaves Lansdown, said: “Savers face a double whammy of a small rise in inflation, and wide-ranging cuts to savings rates in the past month. Over this time, the number of accounts offering more than 2.1 per cent fell by a fifth.

“When fixed rates drop like this, it’s partly a result of the fact that banks think interest rates will remain low, and could be cut further, so they don’t need to offer such generous rates to attract savers for the long term. Increased uncertainty around Brexit, and early signs of weakness in the economy, are likely to be depressing rate expectations at the moment.

“Falling rates underline the fact that beating inflation means being active with your savings. The best way to protect your savings from inflation is to take a portfolio approach – keeping emergency savings of three to six months’ worth of expenses in a competitive easy access account, and fixing the cash you expect to need over the next five years over the periods that suit you best.”

The best 18-month bond is currently offered by the Bank of London and the Middle East (BLME) which pays 2.25 per cent. BLME is an Islamic bank which means this is an “expected profit rate” rather than an interest rate.