The fire destroyed 130,000 business and residential phone lines, leaving companies without telephone links, fax lines and access to their networks.
Vodafone, O2 and T-Mobile mobile phone networks, which rely on BT capacity, were also disrupted, wiping out coverage in some areas of the North West.
Companies from North Wales, Derbyshire, Cheshire, and up to 100 miles away from the Manchester epicentre, lost communications in the immediate aftermath of the fire.
Businesses not directly affected reported that their phone lines were constantly engaged as BT struggled to re-route calls around other parts of its network.
Firms that lost access to computer data invoked their disaster recovery plans and moved staff to remote emergency sites within hours of the failure.
Manchester Chamber of Commerce estimated that, with phone lines still out of action four days after the fire, businesses were losing £4.5m a day.
Manchester Chamber of Commerce chief executive Angie Robinson said, "The fire has paralysed the Manchester business community. The incident has had an obvious affect on the city's new media and knowledge-based industries that rely on the internet and telecoms."
The fire disrupted ambulance radios in Manchester and calls to police 999 services in parts of the North West. Derbyshire police ordered emergency supplies of Orange mobile phones for officers in the Buxton area.
The incident had a "massive" impact on the call centre industry in the North West, said Colin Mackay, director of quality and standards at the Call Centre Association.
Several call centres were forced to relocate staff to temporary offices and others, unable to take incoming or outgoing calls, spent the day training their staff, Mackay said.
High street retailers lost links to the Switch network, and there were reports of some retailers in the Buxton area sending staff home.
Thirty-one cash point machines in central Manchester, which rely on telephone links to communicate with banks, were put out of action by the fire.
NatWest Bank said it was forced to close 16 branches in the Stockport area, after the fire destroyed data links between branches and the bank's Edinburgh datacentre. Lloyds TSB closed 15 branches.
The National Computing Centre was among many Manchester organisations to lose access to its data communications links, website and external phones. Local government IT directors' organisation Socitim also temporarily lost its website.