The government's accounting watchdog has warned the taxman against influencing PricewaterhouseCoopers' investigation into the missing child benefit data discs.

Appearing in front of the Treasury committee for the first time on Wednesday afternoon, HM Revenue & Customs acting chair Dave Hartnett repeatedly said that swingeing job cuts at the department were not to blame for the mass of sensitive personal data to be placed on CDs and subsequently lost.

However, Labour MP Jim Cousins suggested that Hartnett's statements could prejudice PwC chairman Kieran Poynter's review into HMRC's processes and controls: 'We don't want Poynter to be inhibited'.

Hartnett replied: 'There is no intention of us being prejudicial. We will take this issue to him.'

Hartnett also revealed that the estimated cost for stripping the data of sensitive information - which had been suggested to be too expensive for tax officials to remove before sending it to the National Audit Office - was about £50,000.

More to follow.