Former clients of a Suffolk accountancy firm have expressed fury at the news their tax bills to HM Revenue & Customs (HMRC) are to rise due to increases in interest rates.

HMRC has confirmed interest rates on repayments will rise to 4.25% from August 22, having been at 2% at the start of the year.

This has meant several ex-clients of Apostle Accounting, based in Stowmarket, face increased sums to pay back to the tax authority.

A number of former Apostle clients revealed earlier this year they have been told to pay HMRC sums in the thousands of pounds, having previously claimed tax refunds through the accountancy firm.

East Anglian Daily Times: Apostle Accounting's Stowmarket office in Marriotts WalkApostle Accounting's Stowmarket office in Marriotts Walk (Image: Newsquest)

HMRC said it has "a legal duty to recover incorrectly claimed money" and uses the Bank of England base rate when calculating interest owed.

Apostle has repeatedly denied any wrongdoing over the tax refund matter and said HMRC applied the wrong guidance when authorising the payments to the clients in the first place.

Lee Osborne, who has been collating data on former clients of Apostle, said he was "appalled and deeply angered" by the interest rate rise.

He said: "The imposition of crippling interest by HMRC on those affected, compounded by their recent increase in interest rates, is a double blow to individuals who are already grappling with the consequences of engaging with Apostle.

"HMRC's interest charges, alongside their rate hike, are unjust and further compound the injustice.

East Anglian Daily Times: Lee Osborne, a former Apostle clientLee Osborne, a former Apostle client (Image: Lee Osborne)

"If HMRC genuinely aims to stand by the individuals affected by the use of Apostle then they must halt and cancel these exorbitant interest charges and offer true support to those who have worked tirelessly to contribute to society."

An HMRC spokesman said: "We have a legal duty to recover incorrectly claimed money, and to charge interest on all tax paid late.

"The rates of interest applied to tax debts is linked to the Bank of England base rate.

"Taxpayers remain responsible for any claims made on their behalf.

"However, we take a supportive approach to dealing with customers who have tax debts, and do everything we can to help those who engage with us to get out of debt, such as offering instalment plans."