Government departments are still struggling to produce relevant and reliable data on their performance, according to a report from the National Audit Office.

The public spending watchdog examined the data systems used by different Whitehall departments to judge progress on their public service agreements (PSAs).

PSAs are at the centre of the government's efforts to increase efficiency in public services.

The three year agreements are negotiated with the Treasury and set out aims, objectives and key performance targets that each of the main departments are required to meet in return for the funding they receive.

However the report, published on Wednesday, said many departments have failed to develop systems that account for the significant risks to data reliability.

Departments should give more attention to data issues when PSA targets are selected, said the report, and relevant staff should be involved to ensure the right data is available.

Raising the profile of data issues and developing a corporate view of risks to data reliability will help departments monitor and manage systems more effectively, added the watchdog.

Ensuring data systems are properly defined and documented will allow them to be operated more consistently.

And users of performance data need to be aware of the limitations in underlying systems so they can make well informed assessments of the results.

"Good quality data are crucial for the effective use of performance measures and targets in improving service delivery and accountability," said NAO head Sir John Bourn.

"Departments need to devote more attention to data systems if they are to get full value from their performance management systems in the round."