Half a million letters from hospitals to GPs have been lost in the years 2011-16, according to shock new figures from the national audit office.

Jonathan Ashworth, Labour’s shadow health secretary, has described the revelations as a “total scandal”.

The private company involved, NHS shared business services, is part owned by the department of health, which Ashworth warns poses a conflict of interest for the health secretary Jeremy Hunt.

“For a company partly owned by the department of health and a private company to fail to deliver half a million NHS letters, many of which contained information critical to patient care, is astonishing. There remain over 1700 incidents of possible patient harm unaccounted for. This is a staggering catalogue of mistakes on this government’s watch,” he said.

The letters lost include blood test results, cancer screenings, child protection forms and medication changes, according to The Times.

“In total the clear up operation has now cost over £6m and counting. This is an extraordinary waste of taxpayers’ money,” Ashworth added.

“I asked the government in February what they would do to recover this money and they said the costs couldn’t be untangled from the main contract. Given the sheer scale of this incompetence Jeremy Hunt needs to set out what he’s going to do to make sure that NHS patients don’t lose out because of this litany of mistakes and the shady cover up around them.”

“What’s more, the attitude of NHS Shared Business Services, a company part owned by the department of health, has been roundly criticised by the NAO. The company seem to have held back the scale of these problems for several years during which time they were paid tens of millions of pounds to carry out this service. The national audit office say there is a conflict of interest in the secretary of state’s position on the board of this public private venture.”

“The secretary of state needs to explain to the public how he got himself into this conflict of interest, why the oversight of the company went wrong, and why he failed to pick up this string of mistakes for so many years. He should apologise to patients and to taxpayers.”