Harra was particularly angry about the committee’s criticism that HMRC was deliberately degrading the quality of its phone helplines to force taxpayers to go online.

In a letter to committee chair Sir Geoffrey Clifton-Brown, Harra said: ‘I refute these claims in the strongest terms’, adding that the report ‘contradicts’ what he and his team told the MPs when giving evidence on 28 November at a Public Accounts Committee hearing.

‘The committee’s claims about our customer service are completely baseless,’ said Harra. ‘In reality, we’ve made huge improvements to our service standards, with call wait times down by 17 minutes since April last year.

‘We will always be there to answer the phone for those who need extra help. At the same time, more than 80% of customers are satisfied with our digital services, with more and more people using them to quickly and easily manage their tax affairs.’