MPs have warned plans to move HM Revenue and Customs services online could lead to a "disastrous decline" in customer service.
In a report by the Commons public accounts committee MPs said they were "not convinced" HMRC's digital switch-over would not repeat the "collapse" of 2014-15, when call waiting times tripled, the BBC reported.
Currently waiting times are about five minutes with plans to get that down further, according to HMRC.
However, customer service staff are due to be cut by about a third as HMRC expects more people to access services digitally. It has to save £98m by 2021, which means employing 16% fewer staff and closing 137 offices, the BBC wrote.
Having already lost its chief digital and information officer, any more departures of key staff would be damaging, they warned.
"HMRC is staking a great deal on the success of its plans to digitise the tax system, but once again it lacks an adequate plan if demand for its call centres does not reduce as quickly as it hopes."
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