CUTS to helplines set up by the taxman could result in standards of service plunging back to “unacceptable” levels, it has been claimed.

Her Majesty’s Revenue and Customs (HMRC) plans to reduce spending on the services by one-third over the next five years.

MPs on the Commons Public Accounts Committee (PAC) have expressed concern about the proposals and warned that helpline services “collapsed” in 2014/15 due to HMRC underestimating the demand for telephone assistance when it reduced available staff by 5,600.

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It said in a report that HMRC admitted its service levels were “unacceptable” at times and, in October 2015, the average wait to have a call answered reached almost 35 minutes.

More than one-quarter of callers gave up trying to get through in 2015/16, and charges for callers spiralled, with every £1 saved by HMRC cutbacks resulting in additional costs of £4 for people trying to get through.

Callers had to wait a total of four million hours to get help in 2015/16, the report revealed.

PAC chairwoman Meg Hillier said the prospect of further cuts would “chill the blood” of people needing assistance.

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She added: “HMRC’s recent performance in this area has been appalling for long periods and left members of the public counting the cost in time and money. It is bad enough that people trying to pay their fair share of tax should have been kept waiting for so long.”

An HMRC spokesman said: “This is an inaccurate, out-of-date reflection of our phone performance. We acknowledge that service levels in the early part of last year were not acceptable and we apologised at the time.”