Work by the National Audit Office (NAO) led to audited savings of some £1.2bn last year in public spending, according to its annual report and accounts.

The annual report says the NAO certified 437 accounts in 355 organisations, assuring more than £1 trillion, during 2012/13. It also published 63 value for money reports and supported 57 hearings of the Public Accounts Committee (PAC).

The NAO says 82% of PAC recommendations were accepted during the period, and cites its report on HMRC customer service performance as an example of its efforts to improve customer service within the public sector. As a result, HMRC committed to meeting targets of answering 80% of calls within five minutes, introducing more online services and replacing expensive 0845 helpline numbers with 03 numbers.

Nearly two thirds (63%) of bodies audited say that the NAO's work improved their approach to financial management and control.

The accounts show that the NAO has reduced its overall costs by 15% in cash terms (22% in real terms) in the three years since 2010/11.

NAO head Amyas Morse said: 'In providing assurance to Parliament for the way public money is spent, the NAO has a role of critical importance, particularly at a time when money is tight and the public sector is going through substantial change. We continued to play this vital role in 2012/13, developing our insight into the critical, systemic issues facing our clients, and seeing a real impact from our work.'