National Health Service (NHS) IT chief Richard Granger has claimed the costs of the National Programme for IT (NPfIT) he oversees have been inflated.

He said the £12.4 billion price tag now attached to the plan is a figure he agreed to under "significant pressure" from the National Audit Office (NAO).

Granger defended his record and claimed he had been "singled out for special treatment" by the auditors in a frank interview with CIO in this month’s magazine.

The NHS IT chief executive, who has announced he will quit the post before the end of the year, told CIO editor, Janice McGinn: "All sorts of wild numbers are being produced, the best one being £50bn from Tory MP Richard Bacon. At the end of March 2007 we had actually spent £1.5bn."

He claimed: "They [The NAO] went round and added up all the costs they could find and singled me out for special treatment. That's when they came up with the £12bn number.

"Under significant pressure, I and the Department of Health decided to agree to an NAO report that said the total cost of the NHS Programme would be in the order of £12bn."

Granger's suggestion that the NAO had forced him to knuckle under may come as a surprise to members of the House of Commons Public Accounts Committee, who last June expressed scepticism at the "almost universally positive tone" of the NAO report. Greg Clark MP described it as "easily the most gushing" he had seen.

Last month, the British Medical Association demanded a public inquiry into NPfIT.