The quality of government websites, which cost taxpayers £208 million a year, has improved “only slightly” over the past five years, the National Audit Office has said.

A report produced for the public spending watchdog by a joint team from the London School of Economics and Oxford University says use of the main government websites has risen over time, with some sites now being “widely and repeatedly used”.

But many sites are “text-heavy and off-putting to the user”, with complex structures that often make information hard to find among large quantities of policy material that users find irrelevant, the report says.

A third of government departments and agencies had very little knowledge about the cost of online service provision, the NAO warned, while most did not have sufficient information on who their users were or how they used the sites.

The NAO said a consolidation of information onto two “supersites” – Directgov and businesslink.gov.uk – was a promising initiative but warned that this was an ambitious programme that must be carefully managed and kept under review, risks to the giant website carefully monitored.

The move is part of a rationalisation of government websites announced in January that is set to see 551 sites axed.

Edward Leigh MP, chair of the Public Accounts Committee, said getting good quality online information and services was “a promise yet to be fulfilled”.

“When our committee last reported on government on the web we recommended that, in order for departments to increase the number of customers using their websites, they would need to have excellent information on who is using their online services and why. There has been a significant lack of progress in this area,” he said.

The NAO recommended that government departments be required to report annually on the cost of online services using a common methodology.

The government should develop revised standards for its websites and none should go online unless they met accessibility and usability criteria, the watchdog added.