Customers of large UK ISP Plusnet have experienced a morning of disruption after a maintenance upgrade slowed web browsing to a crawl for many.

"We are currently investigating a problem that has arisen during maintenance of our traffic management platform. Customers will likely experience slower speeds than normal due to being assigned a default profile," read a message from Plusnet customer support.

Starting around 8.30am on 2 February, many users were forced to cope with modem-level speeds that could barely web load pages, leading to a stream of complaints on Twitter. At one point the company’s website went down.

By 2pm, web throughput was apparently back to normal although the cause of the problem remained unresolved.

“Our engineers have applied a temporary solution and many customers are reporting that they are seeing speeds improve. We are continuing to investigate the root cause and will update this service status once we have more information,” said PlusNet support.

BT-owned Plusnet enjoys a reasonable reputation among its users, some way ahead of rivals such as Talk Talk which Ofcom recently named as the most complained about broadband company in the UK.

In October, Virgin Media went dark for customers in several Fife towns after rats repeatedly chewed through data cables.