The UK government's ageing IT systems make "extracting data expensive and sometimes impossible" – yet there is no central repository that lists creaking kit in need of replacement, the Public Accounts Committee (PAC) has found.

In its report: Challenges in using data across government (PDF), the spending watchdog said poor data in government has led to failings in services, poor decision-making and an inability to understand how best to improve.

"Issues with data come up in many of this Committee's reports. Over many years government has increased its use of technology and data. However, departments have been left to develop their own processes for managing data, leading to inconsistency across government," the PAC stated.

The PAC, a select committee that oversees government spending, is calling for "a step-change in the government's approach to data", calling this "long overdue."

It noted the Department for Digital, Culture, Media and Sport has announced that it will produce "yet another data strategy." But previous initiatives to improve the use of data across government have not delivered the benefits promised.

"The government has barely scratched the surface of what it needs to do so it can use data to deliver joined-up public services and increase efficiency. This will not be a quick or simple task as there are significant challenges."

These include a lack of government-wide data standards; ageing IT systems; fragmented leadership; and a civil service culture that does not support sharing data across departmental boundaries.

The committee noted that in a report on the troubled Universal Credit programme last year, it found the Department for Work and Pensions could not assess how it treated vulnerable claimants as its systems did not allow this.

"Replacing or modifying government's systems will take time and be costly and needs careful planning. We were surprised that the government does not have a list of its ageing IT systems on which to base its strategy."

The committee asked DCMS how it planned to tackle government's ageing IT systems, which limit how government can use data. "DCMS and Cabinet Office told us that this would take time as it was not realistic to replace all of government's ageing IT in one go."

The PAC urged the Cabinet Office and DCMS to identify the main ageing IT systems that, if fixed, would allow government to use data better. "They should ensure that whenever departments replace or modify these systems this is done with full consideration of how the systems will support better use of data in government."

It also asked about the new data systems the government is developing to prepare for the UK's exit from the European Union.

"We had already heard that some critical data standards were not in place yet, but Cabinet Office assured us that the new systems were being built to other GDS standards, namely its digital service standards and its technology code of practice.

"We pressed DCMS on how it would tackle the challenges of replacing government's ageing IT and whether it had a list of government's systems and the problems with them on which to base its strategy. Neither Cabinet Office nor DCMS has a government-wide list of the IT systems that government will need to upgrade or replace if it wishes to make real advances in how it uses data," it added.

The National Audit Office has previously found that most of government's data resides in its legacy systems, some of which can be inflexible and lead to poorly organised, out of date or inaccessible data that cannot be extracted or shared easily and is costly to combine with data from different systems. ®