The UK government's websites are unreliable in the level of service they provide, according to a report by an internet performance company.

Keynote Systems said that the UK's official websites offer a wide range of response times and availability. 

"It is startling to observe the wide difference in website performance between departments within the government," said Haran Sold, vice president at Keynote Systems.

"With limited budget to enhance their websites, these organisations should be working together to find a model for sharing best practice in internet performance."

The research made embarrassing reading for some government departments, such as the e-Government Unit which came 36th out of 38 sites. 

NHS Direct, which was set up to reduce medical waiting times by providing patients with advice, came just one place higher at 35. 

All of the sites in the bottom five recorded a similar loading time to the 14.54 seconds it took the 37th-placed Foreign and Commonwealth Office website to load. 

The bottom placed site was the Inland Revenue's Tax Assessment portal, which was out of action for the equivalent of almost 10 minutes every hour with an availability of 83.63 per cent. 

However, the Tax Assessment website did state that it was undergoing essential maintenance during the tests.

A Cabinet Office spokesperson said that the Transformational Government document had laid out the government's ambition to improve and focus its presence on the web.

"The Implementation plan set out our plans to review existing presence and reduce the number of website and improve the quality of those that remain," said the Cabinet Office spokesperson.

"Increasingly the focus needs to be around the customer - which is the key reason for the success of Directgov and why, over time, the government will move more services there."

Some sites performed better than others. Her Majesty's Stationery Office recorded the lowest average load time at just 0.29 seconds. 

The Financial Services Authority, the Audit Commission and the Department of Work and Pensions followed closely, maintaining an optimum balance between rapid loading times and maximum availability. 

Despite only coming ninth in the response time tests, the UK Parliament website boasted 100 per cent availability during the whole of Keynote's measurement period.

"The central objective for any online government facility should be to ensure that users can access content quickly whenever they need it by offering lean loading times and high availability," said Sold.

"If this is not in place, users lose faith and sites lack the credibility which is essential to engineer public trust."

A recent survey by Southampton University found that more than 60 per cent of UK government sites contain HTML errors, and only 39 per cent comply with the Web Content Accessibility Guide.