BT users unable to get online for two days

British Telecom is struggling to cope with a series of problems that have effectively prevented millions of UK customers from using the internet over the past two days.

Although the company insisted that an earlier problem which put its high-speed users offline on Tuesday had been fixed that day, millions of people who access the internet via BT phone lines were unable to get connected yesterday. BT initially denied there was a problem. But its main website, Btconnect.com, was unreachable for much of the day, and its helplines were overloaded with callers complaining about the lack of connection.

"I was told by the BT support line that one-third of the country was without access to the internet," said Arthur Pottersman, of C&MC, a London design company. "That was after we had been fobbed off, as usual, by a recorded announcement saying there was a problem but not saying what."

BT said yesterday's crash was caused by difficulties with routers – hardware which sends data to different destinations on the network – while the difficulties on Tuesday, which cut off internet access for thousands of high-speed "broadband" users and all of its million-plus BT Click dial-up customers, was caused by a problem with its "Colossus" network. The reason for this is unknown.

Tony Henderson of BT Openworld, which is in charge of BT internet connections, said it was a problem for BT Retail, the arm of the company which looks after the physical wires. BT Retail said it was a problem for BT Openworld.

When BT Connect's web page finally returned to life late yesterday afternoon, it carried no explanation for the black-out – though its "service status" page, buried in the site, admitted there were "still problems" for users.

The problem did not affect BT telephone lines.