A study of data from 6,000 UK companies with leased line internet connections has shown that nearly 1,000 are losing desktop performance because of insufficient bandwidth.

The chief reason that IT managers tolerate such a situation is that most established browser functions are designed for older and slower connections. Performance slowly falls away, and IT departments wait until the level of complaints escalates before upgrading - if budgets allow.

Another key problem is the prevalence of bandwidth-hungry applications such as voice over IP.

However, companies do stay loyal to leased line connections, primarily because DSL is perceived as unreliable.

Richard Thomas, managing director of software-as-a-service network management firm NetEvidence, which collected the data, suggested that telecoms providers are often willing to strike a bargain to keep customers.

"Service providers are not chasing for upgrades but, if asked to re-price, many will offer competitively priced upgrades," he said.

"New and faster lines are available all the time, and providers are keen to lock customers into fixed contracts to secure their revenues. These customers may find they can get a good deal, and their users will benefit from vastly improved performance."

Poor performance is a particular problem for smaller companies hosting their own web sites, where slow servers could be discouraging business.