The bank has this month sent letters to cash ISA customers who also held a Junior ISA, apologising for not being clear about a cut in interest rates.

As part of its now-closed ‘relationship interest rate’ deal, customers were rewarded with an additional 1% interest on the Junior ISA, so children earned 4% instead of the standard 3% rate.

However, in September 2016, Halifax wrote to these customers to inform them that the Junior ISA rate would reduce from 4% to 3% from December 2016. However, it failed to make clear this change was because the relationship interest rate was coming to an end.

Halifax wouldn’t disclose how many customers were impacted, but said it was a very small percentage of their overall savings customers.

While it hasn’t broken any banking rules or regulations as it specified the correct interest rates and gave savers enough notice of the change, it is apologising and giving customers more information so they understand why the rates were changed three years ago.

A Halifax spokesperson, said: “We are very sorry to the customers who received letters which did not make clear that the change in interest rate was due to their relationship rate coming to an end.

“While the correct rate of interest was included in their original letter, we have recently written to them again to provide additional context and explain the options they may wish to consider.”

They added that where a customer feels they may have been financially disadvantaged, they can contact Halifax using the number given on the letter where it will consider individual circumstances.