Mel Stride MP, chair of the Treasury committee, wrote an open letter to NS&I chief executive Ian Ackerley.

According to NS&I’s own statistics, the six months ending 30 September 2020 saw a 43% increase in complaints compared to the preceding six months.

As well as questions about complaint levels, Stride asked Ackerley to explain the low levels of customer satisfaction with NS&I, the rationale for the dramatic cuts to NS&I’s interest rates on savings products, and the now-postponed decision to stop paying Premium Bond winners by cheque.

Stride wrote: “The dramatic cuts that NS&I have made to their interest rates on savings products have also resulted in significant outflows of deposits in recent months, and a great deal of anxiety on the part of customers. In addition, NS&I’s plans to end payments of Premium Bond winnings by cheque in 2021 may increase risks for vulnerable consumers with limited access to the internet.”

In September NS&I announced that interest rates on several of its savings accounts would be slashed to just 0.01% in November, while Premium Bonds holders would have less chance of winning later in the year.

The following month saw NS&I customers report technical issues with its website and problems withdrawing their money.

Stride said: “Whilst NS&I took steps to keep service levels up during the pandemic, they appear to have been unsuccessful. The decision to stop paying Premium Bond winners by cheque will be particularly concerning to vulnerable consumers.

“I am also seeking clarity around last week’s grant of urgent additional funding from the taxpayer for NS&I. I’ve written to Mr Ackerley to see what reassurances he can provide to the committee.”